Facebook is offering a functionality called Facebook Connect, which allows third party websites to use Facebook as authentication. I was playing a game called "Die Siedler Online" (The Settlers Online aka Castle Empires Online) from Blue Byte / Ubisoft which used this Facebook Connect functionality as option. Sounded good, one click to login via Facebook, instead of having to type in a username and password every time. Only of course now that Facebook disabled my account, I can't login to Die Siedler Online any more either.
I wrote to the Blue Byte / Ubisoft customer support to get access back to my Die Siedler Online account, but got a reply that they were unable to help me. Basically access is blocked by the application on my Facebook account, and unless I delete that application on Facebook, I can't play Die Siedler Online any more. But of course I *can't* delete the Facebook application, because Facebook blocks me from accessing my account. So in spite of not having violated any of the Terms of Service of Blue Byte / Ubisoft, I've been effectively banned from their game as well.
Moral of the story: Do not use the Facebook Connect option on other websites. If ever you get into trouble with Facebook (and they can ban you for playing games with strangers), you also lose access to all other sites you connect to via Facebook Connect. Big Brother is not only watching you, he is actually controlling what you can do on the internet.