How about Ohm's Law? Surely this has got to rate higher than Cowboy Neal's law of missing poll options.

I think it's worth pointing out that the parent poster has had the bottom screen protector scratched up very badly. With everyone that I know, including a family where three people share a DS (for about a constant 7 hours of use a day between them--yes, they're gaming nerds), there has been no damage at all to the bottom screen using fingers or the stylus.

Admittedly, if you wanted to, I'm sure you could damage it if you tried, but I'm fairly sure the screen wasn't built to withstand extended play using a steak knife as a stylus, for example.