I don't see this as often these days - what I usually see is women using their avatars to imply they're sexually crazy, and throwing too much private stuff out there.

It's kind of like posting pictures of your tits... sex baiting, I suppose you could call it?
It's like; being a girl on the internet isn't that impressive anymore, and hasn't been for a while, but being a sexually active girl on the internet?... Wowzers!

Not to demonize the women doing this, mind you, it's just a trend I've noticed. I don't even think people who draw overly attractive avatars for themselves are in the wrong, because who wants to represent themselves as ugly, especially if you're self conscious about such a thing?