Clay Shirky has written an interesting essay called A Group Is Its Own Worst Enemy about “social software” and group behavior. There are lots of interesting points in there, and he does mention good old LambaMOO, but here’s my favorite part:

anonymity doesn’t work well in group settings, because “who said what when” is the minimum requirement for having a conversation. What’s less well understood is that weak pseudonymity doesn’t work well, either. Because I need to associate who’s saying something to me now with previous conversations….
…you have to design a way for there to be members in good standing. Have to design some way in which good works get recognized. The minimal way is, posts appear with identity. You can do more sophisticated things like having formal karma or “member since.”

Hear, hear. Weak pseudonymity has been the death of too many sites to mention, most notably (for me) e-thepeople. The near-total lack of consequences for behaving badly (but not badly enough to get banned) and the inability to distinguish the “core members” of a community from the “drive-by” posters (using Clay’s terminology) inevitably leads to protracted flame wars and nonsense threads. If people have some reason, no matter how slight, to protect their reputation, they’ll behave much more reasonably.