Or, you know, just use a login name with a password? Why do identities need to be connected by default? Who really thinks making up a name and password is too much trouble? Are the Hacker News and Reddit models really so bad?
Facebook: 50% of my (heh.. Hate that site. Admittedly meager selection of 60 friends) have a pseudonym as name. Among my 2nd level friends that's even more common. It's really _uncommon_ to have a real looking name, not some play on words or weird spellings of something that not even remotely resembles your name. Ah yeah - and my privacy settings _should_, unless Zuck decided otherwise lately, make it impossible for anyone to see much about me anyway, so my 'real identity' is worth zilch.