My Facebook wall keeps getting spammed with this "Barack Obama Hillary Clinton Sex Scandal" video. This is apparently propagated by koobface or a similar type of worm.
You need to be really careful with any kind of "watch this video" message that gets posted on your wall. Usually this type of link will redirect you to another site which asks you to download an update of the Adobe Flash player. The "update" is actually the worm, which infects your computer.