> In 2007, we launched the Facebook Platform with the vision that more apps should be social. Your calendar should be able to show your friends’ birthdays, your maps should show where your friends live, and your address book should show their pictures. To do this, we enabled people to log into apps and share who their friends were and some information about them.

Anyone who was in a FB sales meeting when OpenGraph was launched knows this is a very calculated understatement. I've heard them explicitly sell the information of an entire user's friends list to anyone willing to pay.