I can feel hungry, and no matter how much I eat, I still feel hungry. Contrariwise, I can go all day without feeling hungry, and be unaware that I haven't eaten until I pass out from hunger. All in all, my sense of hunger is a completely useless tool for figuring out if I have to eat or not.
Of course, everybody is trying to do this. If I can figure out how to automatically do stuff for Facebook, too, that'd be good. That way, I can post to three sites at once.