Why the switch in strategy? Microsoft says that it’s making Morro a mean, lean product that won’t be too piggy when it comes to system resources, and Senior Director of Product Management Amy Barzdukas is quoted in the release as saying “This new, no-cost offering will give us the ability to protect an even greater number of consumers, especially in markets where the growth of new PC purchases is outpaced only by the growth of malware.”

Which doesn’t really explain why Morro apparently won’t simply be a new version of OneCare, or why free and fee versions can’t coexist. You’ve got to think that it’s in part a confession that OneCare hasn’t been terribly successful in the market place against its competition from McAfee, Symantec and others.

Over at CNET, Ina Fried says that the prospect of a freebie security suite from Microsoft “puts rivals such as McAfee and Symantec in a tough position.” I’m not so sure. The free Windows Defender anti-spyware utility that hails from Redmond doesn’t seem to have inflicted grave competitive damage on third-party security companies. Nor has the firewall that’s built into Windows Vista.

I have no data whatsoever to support this theory, but I sometimes wonder if Microsoft’s reputation for building insecure software lessens the likelihood that its customers will trust the security software it develops. Even if the worst days of Windows security nightmares are behind us, that doesn’t leave anyone with the perception that the name “Microsoft” is synonymous with “ironclad security.”

Anyhow, we don’t know anything about Morro yet other than what little Microsoft revealed today, but I hope it’s good and I’m glad it’s on its way. I don’t think consumers should have to pay to get some minimal level of PC security. And thanks to scourges such as botnets, unprotected PC users put not only themselves at risks but others too. If all Morrow does is meaningfully nudge down the percentage of computers in the world that are vulnerable to attack, it may do more for the world than OneCare ever did.