The other day a friend on Facebook had their account totally deleted. He was actively using his account and had hundred of friends. There have been reports that your FB account can get randomly deleted, but this is usually done on SPAM activity. He discovered the reason for deletion is most likely due to not cleaning out your inbox of messages or sending out too many friend requests. They do not give specific details of why his profile was deleted but they did make one thing clear that the decision is final and you can not appeal.
Have you ever had your Facebook account deleted? What was the reason you were given?