It seems that one of their servers had a mod_php problem and flashed the source code of the facebook main page into a small number of users' browsers. One of those people posted the source code on this blogspot blog. Posting the code is against the law, and Facebook is asking that people not distribute it any further.
mh that last file isn't really much code. just some interface stuff. and even that is pretty boring stuff :D allthough I haven't registered at blogger, no idea what there might be