[bigiain]

> Last I checked it needs a valid email address, name, and password.

And your social graph. You implicitly give it information about all your interactions and connections - and allow it to record even interactions you aren't aware of (like other FB users looking you up or checking your profile without interacting with you in ways you find out about). You're also opting in to web-wide surveillance, where FB track you individually across every webpage with Facebook social widget on it (unless you take steps to manage your browser's FB login status - and most likely even if you do log out whenever you're done with FB by using "industry standard" ad network browser fingerprinting...)