Bruce Schneir has an essay on Wired about anonymity vs. accountability
The problem isn't anonymity; it's accountability. If someone isn't accountable, then knowing his name doesn't help. If you have someone who is completely anonymous, yet just as completely accountable, then -- heck, just call him Fred. History is filled with bandits and pirates who amass reputations without anyone knowing their real names. EBay's feedback system doesn't work because there's a traceable identity behind that anonymous nickname. EBay's feedback system works because each anonymous nickname comes with a record of previous transactions attached, and if someone cheats someone else then everybody knows it.