@irontoenail - Wow, I didn't realize they did so much stuff. I just never really thought about it, I guess. It kind of makes it even worse when people bite their nails too much. I've got a friend who bites his almost down to the quick (the hyponychium, I guess) and he does sometimes make it bleed. I wonder if he would have less sensitive fingertips as a result.
I guess it's just something some people have to live with. Nail biting seems to be pretty common, actually.