Every site today uses social buttons. It's become part of the basic functionality. And yet most have trouble dealing with and integral part of the whole sharing part -- choosing an image to accompayny the shared article.
Facebook has changed their API on the 11th of March, 2011. The main feature is allowing you to create application using iFrames instead of FBML -- which is great! The problem is that I spent half a day for something that should only take 10mins; that is, figuring out what you need to do in order to integrate your custom PHP code with Facebook.