Control Freaks: Via Beyond Madison Avenue's Mack Collier, Coca-Cola is sending half a dozen college students from around the world to blog the Olympics, but it has imposed conditions: nice, happy, upbeat stories only! Says Mack: "[They're] not bloggers, they are members of your PR team. Let them actually post about their experiences, and not type a commercial for the event, then they'll be bloggers."

Coke's a sophisticated company. It can work this out for itself. But there's a continuum in corporate communicaions with credibility at one end and control at the other, and you can't get the former without surrendering the latter. And that's exponentially more true in the blogosphere. This isn't even PR; it's advertising. Coke is paying these kids (at least with travel expenses) in exchange for their favorable commentary.

When are marketers going to figure out that credibility is more valuable than control; that earned praise is more valuable than paid-for self-congratulation?