If you are a Facebook member and like a Facebook page and/or mention a Facecbook page in a wall update, Facebook can use your name and possibly your picture in ads that are shown to your friends.
In fact, your name might be appearing in Facebeook ad now saying that you like a certain brand. Facebook opts everyone into Facebook Ads. And you probably know that because you’ve read Facebook’s Statement of Rights and Responsibilities so carefully
You can opt-out of letting Facebook use your name or profile picture in ads served to your friends by going to Account.
You can read the full version of the blog here.