In January, social gaming behemoth Zynga snapped up the team behind Flock–but not the browser or the company. (Most of the stories about the buyout, including mine, inaccurately said that Zynga had acquired Flock itself.) When Flock CEO Shawn Hardin’s blog post about the news didn’t say anything about the browser surviving, it was ominous. Today, it’s official: Flock is dead.

The company’s history was twisty from the start–it took it about two years to get to the Mozilla-based version I really liked–and while it did attract millions of users, it never became a mainstream hit. I stopped using it regularly some time ago, but I feel a twinge of sadness that its gone. And I’m sorry that Flock doesn’t seem to be explaining what happened: Its home page just says that “Support for Flock browsers will be discontinued as of April 26th, 2011″ and recommends Chrome and Firefox.

(Okay, if the company did explain itself, it would presumably say something like “We couldn’t figure out how to make a business of this.”)

Meanwhile, there’s a new social browser on the block: RockMelt, which is backed by Marc Andreessen, the guy who invented graphical browsers in the first place. It’s based on Chrome and quite similar to Flock; I’m glad it exists but haven’t quite warmed up to it so far.

Hey Flock fans, are any of you reading this? If so, where will you migrate?

The original preview version of Flock, based on the same Mozilla browser code as Firefox, debuted in 2005. (Back then, only students could join Facebook; Twitter didn’t exist, period.) The first beta, which appeared a leisurely two years later, was significantly different and better; I liked it so much it became my default browser. Version 2.0 improved on it further.  But version 2.5, which appeared more than a year ago, was instantly obsolescent: It was based on Firefox 3.0 even though it appeared only shortly before Firefox 3.5 did, and there were rumors that Flock’s creators planned to dump Mozilla and move to Chromium, the open-source version of Google’s Chrome.

Fast forward to right now. It turns out that the rumors were true: Flock 3.0, which is now available as a beta download for Windows, is built on Chromium. Pretty much by definition, that means it’s significantly different from any version before it. But it turns out that the company hasn’t even tried to recreate the old Flock. This isn’t so much an upgrade as a reboot–an all-new answer to the question “What should a social browser be in 2010?”

The list of Flock features that are gone is much longer than the one of those that are still around: It’s lost its Media Bar image browser, built-in blogging tools, integrated Facebook chat and other Facebook-related features, MySpace support, some of its options for routing updates between social networks, and more. I’m sure that some folks who already love Flock–it has 7.5 million users–will find the new version jarring and unsatisfying. The company isn’t abandoning these people altogether: It’s released a Mozilla-based Flock 2.6 that incorporates recent security fixes, and says it’ll consider releasing an update to old-school Flock built on Firefox 3.6.

But from now on, the Chromium-based Flock will be the center of attention. Flock CEO Shawn Hardin told me that the company made the switch to get on a more modern, efficient browsing platform; he says it’ll be much easier for Flock to keep pace as Google improves the Chrome/Chromium platform than it was with Mozilla. (The Mac version, however, requires some extra work: Hardin says it should be out later this summer.) As before, Flock isn’t aiming to topple the world’s most-used browsers, but Hardin says the company would like to see that 7.5 million user base grow tenfold in the years to come, and he thinks Chromium will help get it there.

This new browser feels very much like the close cousin of Chrome that it is, with the same WebKit rendering engine and a similar minimalist interface. (Actually, it’s even a little more minimalist, cramming Chrome’s two menus’ worth of options into a single menu.) Flock 3.0 has Chrome features like Incognito private browsing (here called Stealth Mode) and worked perfectly with the Chrome extensions I tried. And while it didn’t run the SunSpider JavaScript browser as fast as Chrome when I compared them, it sure feels zippy enough–much more so than the old Flock ever did.

Old Flock aggregated updates on your friends’ activities into a sidebar to the left of the main window. In new Flock, the sidebar is on the right, where it’s less distracting, but the basic idea is the same. You can also post Twitter and Facebook status updates, share the current page (with automatic Bit.ly URL shortening). and reply to your friends’ updates from this sidebar.

Wanna find what your pals are saying about a particular topic? The sidebar had a search field. But Flock also cleverly builds friend search into its address bar: Start typing into it, and you’ll see results from Google, your history, and Favorites, just as in Chrome–but also links to status updates from your friends that contain the keyword(s) you’ve typed. A page called Explore lets you see more of these status updates at one time.

(Speaking of search, Flock 3.0′s Chromium underpinnings aren’t its only new Google connection: Google is now the default search engine, replacing Yahoo. Yahoo fans can opt to switch back.)

Flock’s other major social feature-and its most innovative idea–is all-new. Groups let you collect related people (from Facebook, Twitter, Flickr, and YouTube) and RSS feeds using “Cards.” A Group could contain all your high school buddies, for instance, or an assortment of people and feeds relating to sports. You do the collecting via slick search and drag-and-drop tools which also let you combine multiple people from different accounts onto one card–a handy way to merge the multiple personalities of someone you know on Twitter, Facebook, Flickr, and/or YouTube in one place.

Groups and Flock’s Favorites are services as much as they are software: They automatically synchronize their data among all your copies of the browser on every computer you use, assuming you’ve signed up for a Flock account.  Having a Flock account also gives you access to a new feature called a Flock Profile, which gives you a public page on the Web with updates from services you’ve enabled in Flock, Favorites you’ve elected to share, and other links you choose. (Here’s mine.)

Flock Profiles remind me of Google Profiles, which incorporate Google’s controversial Buzz. But I don’t think anyone will accuse Flock’s version of violating anyone’s privacy: They only appear if you turn them on, and don’t disclose your Groups or otherwise display information about your relationships that isn’t otherwise public.

In this beta, Profiles do seem to be buggy. When I looked at mine in Flock, the only Twitter updates I saw were my retweets; in IE, I got non-retweets, too…but my Facebook updates were missing. They’re also a tad spartan–you can’t even upload your photo. But if Flock builds out the idea it could be cool.

Profiles aren’t the only part of the new Flock that feels spartan. I understand and approve of its creators desire to build a Flock that’s more in line with today’s streamlined, lithe browsers than its somewhat bloated predecessor. But even though I’m willing to give up much of old Flock’s bevy of features, I wish the new one had at least slightly richers Twitter and Facebook support. For example, I don’t see straightforward ways to perform basic jobs such as checking Facebook friend requests and Twitter direct messages–two essential tasks that were a cinch in old Flock.

Despite the 3.0 label, this is really a 1.0 product. It’s a nice one–nice enough that Flock has a good chance of becoming my browser of choice again, several years after I found myself using it less and less. But I’m at least as interested in Flock 3.5–or whatever the next significant update will be called–as I am in this beta. I hope it isn’t too far off–a Chromium Flock that added back some of the old version’s richness without the bloat would please both existing aficionados and lots of people who have yet to give Flock a try.

All of which means that Firefox 3.5–which Mozilla plans to formally release today–is no longer a shoo-in for the distinction of being the favorite browser of browser fans. (As I write, Firefox 3.5 hasn’t replaced 3.0 yet on the Firefox home page, but the Windows and Mac versions are live on Mozilla’s FTP site.)

After having spent months with various pre-release versions of 3.5, though, I’m convinced that The Little Browser That Could remains the best choice for the widest array of folks. That’s as much for the virtues that Firefox has possessed for years as for new stuff: Version 3.5′ s improvements are about better speed, useful tweaks to existing features, catchup with other browsers, and early support for emerging Web standards. In other words, the browser sports no knockout new features. But the moves Mozilla has made are smart, and they’re more than enough for Firefox to keep pace with its fast-evolving rivals.

After thr jump, a look at what’s new in rough order of importance.

Speed

In many ways, today’s browser race really is a race: The single biggest trend in recent browser updates is an emphasis on speed. More specifically, an emphasis on optimizing JavaScript, the programming language that’s used on virtually all Web sites and which gives sophisticated Web apps such as Gmail much of their power. For Firefox 3.5, Mozilla created a new JavaScript engine, which it calls TraceMonkey. I used the industry-standard SunSpider benchmark, and found that TraceMonkey is zippy–2.6 times faster than the old Firefox JavaScript engine, essentially tied with Safari for second place, and just a smidge behind Google’s Chrome 2.0.

Here are SunSpider results for Firefox 3.5, Firefox 3.0, Internet Explorer 8, and the newest Chrome and Opera betas–they’re the average of three passes performed on a Lenovo ThinkPad SL300 with a 1.8-GHz Core 2 Duo and 2GB of RAM, and are in milliseconds. Shorter bars are better:

I don’t want to exaggerate the importance of fast JavaScript–it’s only one factor that determines whether a browser feels snappy or not, and you’d be nuts to make it your primary criterion when choosing a browser. (I still wish Firefox 3.5 launched faster, and the Release Candidate version, at least, can still bog down if you open too many tabs.) But JavaScript performance is a big deal, and TraceMonkey gives Firefox a noticeable speed boost.

Privacy

Firefox 3.5 introduces a private browsing option–often called a “porn mode” and usually touted by browser companies as having many other uses, such as letting you hide the holiday shopping you’re doing for your family or borrow a friend’s browser without messing up his or her history. (Then again, Microsoft seems to have given up and is running an IE ad pitching InPrivate as a way to avoid seeing your spouse’s nauseating fetish porn.)

Mozilla calls its private browsing feature…Private Browsing. It’s largely similar to its counterparts in Chrome, IE, and Safari, except that Firefox closes all your open tabs when you begin to browse privately, then restores them when you’re done. It’s a logical way to demarcate things, and probably helps remind you to leave private mode when you’re finished, although reloading your tabs can take a while if you’re as much of a tab freak as I am.

None of these browsers’ privacy features are exactly foolproof–the video-downloading feature in RealPlayer, for instance, helpfully keeps on logging all of the videos on pages you visit even when you’re in a privacy mode. Keep that in mind if you’re paranoid about keeping your online wanderings under wraps.

A new “Forget About This Site” option is a sort of retroactive form of Private Browsing that lets you remove evidence you’d visited a site after the fact. But it’s pretty buried: I could only find it by pulling up the History browser, then right-clicking on a page.

Rather than making erasing your browser’s cookies, cache, and other items an all-or-nothing affair, version 3.5 lets you delete changed for just the past hour, two hours, four hours, or day. Only Chrome does something similar, but its time frames are less useful, since the smallest one is “last day.”

Minor New Features and Tweaks

Firefox 3.5 adds a bunch of small new features and refinements to existing tools, most of which feel like they’re aimed at advanced types. You can now drag a tab out of the window to turn it into a new window of its own, and reverse the process by dragging a window back into tab form. The excellent Awesome Bar address bar, which lets you do search, pull up bookmarks, and retrieve pages from your history, has rid itself of a slight lag it sometimes suffered. It’s also added a really geeky power-user feature: filters that let your refine results as you type by entering “world #”, for instance, to show only pages from your history.

Two new options on the History menu let you re-open tabs and windows you’ve recently closed. I’ve been known to zap a tab by mistake, so if I can remember these items are there, I’ll use them.

Flock’s defining virtue is its built-in support for social networks, media sharing sites, and blog platforms–everything from Facebook, Myspace, and Twitter to Flickr to WordPress. All of version 2.5′s additions involve more creative integration of external services such as these. The most notable one is probably its greatly expanded suite of Twitter-related features, which go far beyond the modest Twitter functionality in previous versions of Flock. You can tweet and retweet, view tweets, @mentions, and direct messages from your followers, and have your long, unwieldy URLs automatically converted into TinyURLs. Flock’s “My World” home page now sports a widget that lets you search Twitter and save your favorite searches (I wish this capability was built into Flock’s left-hand sidebar, too).

Essentially, Flock is now a full-fledged Twitter client, and while it doesn’t sport advanced features such as TweetDeck’s groups, it does quite a bit and does it well.

Version 2.5 also introduces instant messaging to the Flock mix for the first time, through support for Facebook Chat. The implementation is elegantly simple: The strip of Facebook Chat tools that sits at the bottom of Facebook itself now shows up at the bottom of your Flock window no matter which Web page you’re on. I’ve never warmed up to chatting on Facebook–I don’t stay on the site all that long, and my brain has trouble dealing with the notion of an IM client that lives within a single online service. But Flock’s Facebook-everywhere feature may get me chatting more often. (For now, Facebook Chat is Flock’s only native IM service, but the company says it intends to add other popular ones over time.)

The last major new feature is something Flock is calling Flockcast, although in its current incarnation, “Facebookcast” might be a more accurate moniker. When you perform various task on certain services–such as updating your Twitter profile or uploading photos to Flickr–you can choose to have Flock update Facebook to reflect your off-Facebook activity. The Twitter dialog box above shoes the “Also broadcast to Facebook” option, and here’s a snippet of my Facebook profile showing that the party photos I uploaded to Flickr show up as thumbnails on Facebook, with links to Flickr:

I’ve heard more than one Flock doubter dismiss the browser as not offering much that you can’t cobble together in Firefox through plugins and other tweaks. That’s not entirely true, but it’s also a tad beside the point–everything that Flock does can be done through other means. The browser’s unique value stems from its mostly-slick integration of lots of social features into one user interface, with no customization required. (It does, however, result in a fairly crowded environment, especially compared to Google Chrome’s minimalism–Flock is a lot less pleasant on my Asus EeePC netbook than on machines with more screen real estate.)

All in all, Flock 2.5 is a slick upgrade to a cool, useful piece of software. My biggest reservations about it relate not to the browser itself but to the fact that it’s built on top of Mozilla—a design decision that has multiple benefits (you get most of Firefox’s goodness) but also presents some challenges. Most notably, Flock’s development schedule is completely different from that of Firefox, which can leave Flock users waiting for the latest Firefox features.

When Firefox 3.0 was released, the Flock folks responded with a beta version of Flock built on the 3.0 underpinnings with impressive speed. This time around, Flock 2.5 is appearing not too long before Mozilla plans to release Firefox 3.5.  But Flock CEO Shawn Hardin told me that the company is still formulating its plans for what comes after version 2.5, and isn’t ready to talk about a Firefox 3.5-based edition of Flock. In fact, when I asked him about rumors from last March that Flock intended to dump Mozilla for Google’s Chrome platform, he said that everything was up for consideration at this point, including jumping to a new platform.

(My uninformed guess is that it’s unlikely that Flock would have hatched definitive plans to adopt Chrome at this point, given that Flock runs on Windows, OS X, and Linux–Chrome’s OS X and Linux editions aren’t out yet, and there’s no public timetable for their release.)

A next-generation Flock that kept its Mozilla underpinnings could be just fine; so could a Chrome-based one. One of the nice things about browsers is that hopping back and forth is a cakewalk. So if you’re already a Flock fan, or it sounds intriguing, I wouldn’t hesitate to try version 2.5. Still, if I were a Flock user who couldn’t live without Firefox extensions, I’d be rooting for the browser to stick with Mozilla–and I hope that Flock either decides to stay with Mozilla (and moves to Firefox 3.5) soon, or tells the world that it’s going to make the transition to Chrome.

Arrington says that the Flock folks feel like they don’t get enough love from the Mozilla team, and while I don’t know if his scoop is the real deal and have no insider info on the back story here, I do recall once asking the Mozilla team a question that involved Flock, and feeling the tension in the room ratchet up a notch. It’s hard, of course, for Mozilla to both keep busy spreading Firefox and also help a Firefox rival like Flock be successful. But Flock might face the same challenges if it ends up working with Google. We’ll see.

A Chrome-based Flock could potentially have some upsides–the current version, like Firefox, is slow to load (on my Mac, anyhow) and sometimes feels piggy when it comes to resources. Chrome’s emphasis on efficiency could result in a meaner, leaner Flock. (At the moment, Chrome is Windows-only while Flock also speaks OS X and Linux, but Chrome’s support for those two OSes will likely be ready long before a Chromed Flock is complete.)

But if Flock does go the Chrome route, it has one major implication for current users: Right now, one nice thing about Flock is that it runs nearly all Firefox extensions just fine. There are surely Flock fans who, if forced to choose between sticking with Flock and keeping their favorite extensions, would keep the extensions and switch to Firefox. Given that Flock remains a cult favorite rather than the mass-market hit its creators would like it to be, it would be a shame if the lack of extensions bummed out too many of its existing users.

I’ve asked Flock if it has any comment on all this, and will report back…

Update! Here’s a statement from Flock CEO Shawn Hardin:

Flock hasn’t ceased development efforts on the Mozilla platform.  Our upcoming release of Flock 2.1 is built on the Mozilla platform. Having said that, the browser space is heating up, and we’ve seen a variety of new technologies emerge over the last several months that are appealing.

We always have and will continue to make architectural decisions that balance what’s best for our users and what’s best for Flock as a business.  This has resulted in a healthy, growing user base and business for Flock, and we expect this to continue in 2009. In fact, with almost seven million downloads almost entirely from word of mouth, Flock enjoys a highly satisfied user base (consistently over 92% customer satisfaction, with very strong net promoter scores, and an average of four hours of usage per day).

With a continuing focus on user-centered browser innovation, our team is in active research and development on a range of exciting new enhancements to Flock.   It is still far too early to comment on anything specific, but we are very excited about this design phase.

That’s not an acknowledgment that Flock is switching platforms, but it also falls very far short of the commitment to Mozilla you’d think Flock might express if TechCrunch’s report was hooey. It’s not startling that there’s going to be a Flock 2.1, or that it’ll be built on the existing Mozilla underpinnings–if Flock is indeed moving to Chrome, it’s going to take awhile, so an interim Mozilla-based update makes sense.

As before, Flock is a browser for folks who are major fans of social networking and media sites: It’s got built-in support for Facebook, Twitter, Digg, YouTube, Flickr, and other services that let you do things like update your Facebook status and check your friends’ statuses without going to Facebook, Digging stories without going to Digg, viewing your buddies’ Flickr streams, and so forth. Much of this is done through Flock’s People sidebar, which sits to the left of the Web page you’re on so your social tools are always available:

Flock also has the Media Bar, which sits on top of the page you’re on and provides an alternative way to browse videos and images at Flickr, YouTube, and other sites:

I’ve been using the beta version of Flock 2.0 for months, and the biggest news about it is that it’s based on Firefox 3.0 and therefore has all of that browser’s goodness, including the Awesome Bar, new security features, and  better speed and reliability. I had worried that it would be tough for Flock to move from Firefox 2.0′s platform to 3.0, but they did it in a matter of weeks, and it worked well even in beta form. (I hope that they move jut as swiftly to incorporate the improvements from Firefox 3.1, which was released in beta form today.) And one of the best things about Flock is that almost all Firefox extensions work with it, so it’s one of the most customizable browsers on the planet.

The final version of Flock 2.0 adds some stuff that wasn’t in the beta I’ve been using, including support for MySpace and the ability to skin the browser with Themes. It’s also the first browser to support Media RSS, an RSS variant that lets you subscribe to media streams. There aren’t many major sites that offer Media RSS feeds (SmugMug and Blip.tv are two), but if the standard catches on, Flock is ready.

Using Flock is a bit of commitment, since it’s so rich in features and tools that its interface is bursting with icons and dialogs. (I haven’t even mentioned some of its capabilities, like the built-in blogging and the ability to check Webmail accounts from Flock’s toolbar.) In a way, its philosophy about browsing is the opposite of Google Chrome’s: Chrome wants to be so mean, lean, and unobtrusive that you forget you’re using it, while Flock wants to provide lots and lots of tools for helping you get the most out of your favorite sites.

Bottom line: If you’re not a serious user of social networking and media sides, you don’t need Flock–just get Firefox 3.0, and you’re good. But if you do love the Web’s social and media aspects, you might love Flock as much as I do.

Which is not to say that I love it unreservedly.  The support for external accounts is sometimes a bit flaky: For instance, it occasionally forgets an account I’ve added already, and makes me reregister it before it shows up in the People sidebar. And the Webmail feature confusingly shows my Gmail account twice at the moment–once logged in, once logged out:

Despite the odd glitch, I’m a fan. I’m pretty promiscuous when it comes to browsers: On any given day, there’s a chance that I’ll use Flock, Firefox, Safari, Internet 6 and/or 7, and maybe even Opera. So it’s saying something that Flock has been my default browser on all my computers for a year now. If that ever changes, I’ll let you know…

“Flock does a good job at the tasks it sets for itself, but I would recommend it for only the heaviest and most impatient social networkers. For most others, Flock is overkill.”

Oddly enough, even though I spend most of my time in Flock these days and like it a lot, I can’t quibble with that assessment. In fact, when people ask me what browser to use, I recommend Firefox just as often as I do Flock–and if the person in question isn’t into social networking and media sharing, I tell them without hesitation that Firefox is their best option. (Walt takes Flock to task for being busy, and he’s right: For folks who want to take advantage of all its features, dealing with the clutter is worth it, but it’s probably intimidating and unneccesary if you’re not already a pretty sophisticated user of the Web.)

The best thing about Flock 2.0 is that the Flock crew quickly came out with a version built on top of Firefox 3.0. When that browser came out, I was worried that I wouldn’t get the 3.0 goodness for months, if at all–but I’m enjoying features like the Awesome Bar as much as if I was using them in Firefox rather than Flock.

I’ve said this before, but we live in a wonderful era for browser fans: Between Firefox, Flock, Safari, Opera, and, yes, Internet Explorer, there’s something for everybody, and nearly all sites that matter work equally well in all of them. (Exceptions remain, such as the inexcusably IE-only Walmart Music Store.) If Flock sounds intriguing, there’s no downside to downloading it and giving it a whirl. I agree with Walt that it’s overkill for a lot of people. But for some of us, it’s exactly the right browser, and I hope it’s successful enough to be around for a very long time.