I dont care if it's a law or not, but i can't think of a good enough reason not to wear one. I've broken 4 helmets in my lifetime; 2 of which would have caused some pretty serious damage had i not been wearing one. Those 4 reasons are more than enough incentive to make me want to wear one.

Why a helmet over everything else? Because i consider my brain my most important organ....it's not just a part of my body; it's what controls everything i do and allows me to interact with the world. Hell, it's what makes me, me. I think its worth a few extra degrees on a hot day and some dorky helmet head when i take it off. Im not that vain.