If you're sitting on the Yahoo! (Nasdaq: YHOO) board of directors, don't be alarmed at the nature documentary film crews moving in for a close-up. They're working on an endangered species special.

Smile.

Don't take it personally. Carl Icahn just wants to replace the entire board, to try to send a message that investors aren't happy with the way things ended with Microsoft (Nasdaq: MSFT).

Given the choice -- and perhaps a more modest board -- investors will have to decide if Microsoft's offer for as much as $47.5 billion is enough.

Icahn is proposing a full slate of directors ahead of this summer's shareholder meetings. His nominees include former executives at Time Warner (NYSE: TWX), Nextel Partners -- now of Sprint Nextel (NYSE: S), and Viacom (NYSE: VIA). The most intriguing name is Mark Cuban. It's not just that he's more colorful than a Crayola factory or as passionate as a Mexican telenovela. He was one of the first to milk billions from Yahoo!, when he sold Broadcast.com to the company at the peak of the dot-com boom. Can he ride the same horse, one last time?

You know what's missing in all of this? Microsoft. Icahn is playing matchmaker, but we don't know if Cupid has two arrows in its quiver. The $31-per-share offer was real, but quickly declined in value as Microsoft's stock fell. The $33 offer was only presented orally.

Icahn has been building up his stake in Yahoo! -- now 59 million shares and counting -- but Microsoft hasn't gone public with its support. Remember that Microsoft's offer was based on a friendly deal. A new board may lead to more than just turnover in the boardroom. If executives walk and advertisers balk, how much is Yahoo! still worth to Microsoft? Investors need to know that as they hop on Icahn's coattails into Yahoo! 

Unless Icahn and Microsoft CEO Steve Ballmer have exchanged winks, there is always the possibility that Icahn gets the board turnover that he covets but not the exit strategy that he ultimately seeks.

In that case, you may as well begin smiling before the nature documentary film crew, too. It's working on a wildlife piece this time, and you better pray that you're not prey.