Matthew Baldwin is a genius:

Speaking of this, you know what I think they should do? I think they should make it so if you press an elevator button that's already lit, it goes off. This would serve two purposes.

First, it would allow a rider to cancel a button pressed in error.

Second, it would thwart those A-personality types who enter the elevator and press the button for their floor even when it's already lit. This would obviously be the greatest boon of the technology, because, as we all know, those people are totally fucking annoying.

The "this" link goes to a post on Matt's other blog, Tricks of the Trade (which I just added to the blogroll because it, too, is sheer genius). Apparently there's a way to get most elevators to go straight to your floor without stopping for anyone else; evil, but useful.