+ another, at least on forums you know it will be reasonably like minded people, and you can give as much or as little of yourself as you want. I'm quite willing to believe facebook is an information harvesting tool... but it goes along the lines of asking if you are a member of a terrorist organisation at US immigration... how dumb do they think people are?
It does contravene the Data Protection Act - personal info should only be kept for as long as necessary...and if you are no longer using the site, it's no longer necessary, so you should be able to get them to close it completely.