12. IBM and Microsoft

Frenemies since: 1981, when Microsoft provided the DOS (which it had in turn licensed from an obscure software company) for IBM’s first personal computer, helping to make the IBM PC the industry standard and thereby creating the Wintel platform that would go on to put billions of dollars in Redmondian pockets.

Acts of friendship: Big Blue and Bill Gates’ company continued to collaborate on DOS development for years; in 1985, they teamed to create OS/2, meant to be DOS’s substitute; IBM’s famous ThinkPads run Microsoft software to this day, even though they’re no longer IBM products.

Acts of enmity: In 1990, Microsoft abandoned OS/2 and poured resources into making Windows into an OS/2 rival, to enormous success; a ticked-off IBM responded by pouring resources into making OS/2 into a Windows rival, to…well, not much success at all, even though it marketed it as “a better DOS than DOS and a better Windows than Windows.” IBM continued its anti-Microsoft combat when acquired Lotus in 1995, picking up SmartSuite (which completed with Microsoft Office) and the Domino/Notes messaging platform (which still competes with Exchange and Outlook).

Current state of the frenemyship: IBM not only no longer makes desktop operating systems, it doesn’t even make computers that run them. It still seems to derive pleasure from tweaking its onetime best friend, though–just last week, it announced a “Microsoft-free” Linux software environment.

(Microsoft OS/2 disk image from Wikipedia.)