Shii's essay on the strengths of anonymous communities is still the best I've read on the topic. It comes off as somewhat naive, being written in 2004 and updated in 2006, before 4chan had really exploded in popularity and set in stone what people think about when they hear the word "anonymous," but I think his assessment is still valid even in the 4chan of today. Forcing users to check their vanity at the door really does cut down on the superfluous garbage and keeps the conversation about the topic (or wherever the topic meanders) and not about the people having the conversation.

If I could add a postscript to that essay, I'd say that it's 4chan's lax administrative policies, distaste for moderation and censorship, and the incredible size of the community that give it its unruly flavor, not the fact that the posters are anonymous. In the smaller, more carefully moderated anonymous communities I've been a part of, things are much closer to the ideals shii describes.

http://wakaba.c3.cx/shii/shiichan