http://www.urticator.net/essay/0/48.html
Might be a useful read apropos of Wei Dai's recent question:
Why are we causing [people] to think of LW in terms of identity in the first place, instead of, say, a place to learn about and discuss some interesting ideas?
I suspect that those may contribute to the identity-forming tendencies of LW participation, but I think a great deal of the work is already done by the fact that LW as a community deviates so significantly from mainstream cultural norms. I suspect that qualities which set people apart from the majority are more likely to become incorporated into their identities (for instance, a homeschooled person is more likely to think of themselves as a homeschooled person than a person who went to public school is to think of themselves as a public schooled person.)