I would encourage every Facebook user in the UK (or EU, and I think the US has something similar) exercise their rights under the Data Protection Act and request a copy of everything the company holds regarding them.
It is your right. And if you later find that Facebook hasn’t disclosed [I]everything[/I] (which should include what it has bought in from others) within the mandated timeframe, then they are breaking the law.
Actually, we should all do this simultaneously regardless of whether or not one has an account - it’ll cause a national shortage of 80GSM A4 within a week. Just think of it as a bit of ‘work creation’.