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Within 24 to 48 hours was the prediction an hour or so ago, but inside sources say the deal is done and Microsoft sealed it. Numbers have not yet been released*, but Microsoft has apparently beat out Google for a stake in Facebook and will continue to serve advertising.

Microsoft already had a deal to serve ads at Facebook until 2011, and was rumored to be extra-aggressive this time around when competing against Google for a property, after missing out on MySpace, DoubleClick, others.

Former Microsoftie Robert Scoble says it was most likely Brian McAndrews, CEO of aQuantive before Microsoft bought the company for $6 billion, that sealed the deal.

Additionally, CNet is reporting that an anonymous source has confirmed the deal was won by Microsoft. Valleywag has its own methods of confirmation, noting that head of Facebook PR Brandee Barker recently added Microsoft head of global sales and marketing Adam Sohn to her friends list.

Maybe the official announcement is expected in the next day or two, but word on the street says Microsoft finally won one, and it probably cost them up $1.5 billion for a minority stake.

*UPDATE: The Wall Street Journal is reporting that Microsoft shelled out $240 million for a stake in Facebook, which means the company got off cheap, Facebook isn't worth as much as thought by some, or Microsoft bought less than a 2 percent stake.