A recent eWeek piece that runs through some perspectives on Microsoft's recent deals with Yahoo and AOL:

Matt Hicks

[from IM Interoperability: It's the Business Model, Stupid]

Their decision to leave the enterprise market signaled a shift in focus for the large IM networks and helped set up a scenario for greater cooperation with enterprise software companies such as Microsoft, Boyd said.

"The business issue was formally formerly strategic, and that was because they wanted control of their brand and their market in enterprise space," Boyd said. "But now they've rethought it. … Now, they're thinking tactically."