I am not in favour of sharing too much info with Facebook, but if you explicitly agree to give away your data and are not being misled then caveat subscriptor, if you ask me. Some dude from Sophos disagrees:
Right now Facebook is not obliged to force its users to understand what they are signing up to.
How do you "force" someone to understand what they are signing up to?
It reminds me of one of my favourite Simpsons clips: