Kill the username while you're at it.
Mat Honan at Wired is all on about Kill the Password. He's right.
But what about the username? That could use some killing too.
I just made an account with a random username on a site, and all I'm thinking about is finding excuses not to go back, so I don't have to remember a stupid username that's not "dmarti".
Just use email addresses, and let people set a real name or nickname for display if they want.
Yes, I ignore registered user counts from sites that use usernames. They're all (1) people who signed up just so they could "squat" their chosen username, and never come back and (2) people who have signed up a bunch of extra times because they can't remember the stupid username.