While I get it I don't really see the big fuss. Facebook knows as much as you choose to tell it. I choose to tell it nothing. Yes you can infer soft networks from the email address books they've harvested etcetc but really there's nothing in those that can't pieced together if someone wants to anyway. As far as I'm concerned Facebook's a busted flush unless you want to advertise to a slightly below average income demographic with too much time to play mundane online games and from a professional perspective a FB message or email address is about as serious as a hotmail.com one. The inevitable social network market fragmentation is already underway, I'm excited to see what it brings.
facebook also knows as much as your 'friends' choose to tell it about you unless you're vigilant and remove their posts to your wall or untag yourself and so forth.
