Last Saturday afternoon, Microsoft CEO Steve Ballmer sent a stern missive to Yahoo’s board of directors to wake up and smell the $31 a share. (Or $29, depending on how you interpret the letter.)

Microsoft’s call to action not only forced Yahoo (YHOO) to scramble for last-minute alternatives, it also sucked in nearly every major online player to get involved. Just four days after Ballmer posted his letter online, Yahoo got busy brokering a three-way deal to team with Time Warner’s AOL (TWX) and possibly share search-ad revenue with Google (GOOG). Meanwhile, Rupert Murdoch’s News Corp. (NWS) may align itself with Microsoft (MSFT) in effort to bid for Yahoo.

In the rapidly changing landscape of online advertising, the news was greeting with shrugs.

Yahoo’s last stand

The online advertising landscape is a complex, confusing circus where everyone is doing business with one another.

partners finding themselves in alliance.

he rapidly changing landscape of online advertising

no one wants to get left behind and everyone wants to get in each other’s space. Consider this. Yahoo is currently testing a Google owns a 5% revenue share with AOL. AOL

many media companies are becoming agencies, brands are becoming media companies and agencies are becoming technology companie

“These are the kinds of things that force markets to change. These big companies don’t work fast enough to do wild, crazy things,”

“Clearly this illustrates they’ll all been thinking about this all along and an opportune time came to put it into action,”