The Silicon Valley rumor mill has been buzzing with stories about Facebook’s latest negotiations. Some think Google (GOOG), some think Yahoo (YHOO), but signs have long pointed to Microsoft (MSFT). Last Friday, CEO Mark Zuckerberg reportedly met with Microsoft (MSFT) CEO Steve Ballmer at a Palo Alto hotel near Facebook headquarters. Previous reports noted that Facebook founder Mark Zuckerberg was in the Seattle area visiting Microsoft almost three weeks ago. (We’re awaiting comment from Microsoft.)

A Facebook spokesperson  says she is unaware of a Wednesday board meeting. Facebook investor David Sze won’t comment either way.

Should the decision be made tomorrow morning, Zuckerberg would have juicy news to deliver when he makes his afternoon keynote address at the Web 2.0 summit hosted by technology impresarios Tim O’Reilly and John Battelle.