I've stayed out of this debate because I'm one of those private type of persons that Spike was talking about, so I've never had a Facebook account. Facebook is so big and powerful that they can pretty much do what they like with the stuff you post and the information you give them, and that's why they want you to join.
Regarding the real name policy, you can read Facebook's own page on the subject here. You can use nicknames, but, as I understand it, your profile would be headed "Your Real Name (RogerDuke)". Facebook's real name policy is unpopular with a lot of people. Besides those who want to use nicknames and screen names, the policy also creates huge problems for Native Americans, and they don't want the Irish population using the Irish version of their names. A couple of years ago Facebook also blocked residents of a townland called Effin in Co Limerick, Ireland from using their own address. In that case, Facebook eventually gave in - see here. The Wikipedia article about the real name controversy is here.
In the end, I always come back to this cartoon: