Check out this
post from Schneier on Security:

"I’ll be the first to admit it: I know next to nothing about MySpace or Facebook. I do know that they’re social networking sites, and that — at least to some extent — your reputation is based on who are your "friends" and what they say about you.

Which means that this follows, like day follows night. "Fake Your Space" is a site where you can "hire" fake friends to leave their pictures and personalized comments on your page." (from: Hacking Reputation in MySpace and Facebook)

Read the whole thing: Hacking
Reputation in MySpace and Facebook