A male or female that uses facebook as a means of randomly hooking up with other people. Hooker would imply that some sort of currency was exchanged for any service provided both sexual and non sexual. In this case, you usually pay for it in the end with said person you met on facebook in some form or another.
Hey man, check out this chick that I hooked up with through facebook. She turned out to be a real Facebhooker!