I'm in the make-it-mandatory camp. Partly it's cuz I work for hospitals that get stuck for the cost of caring for head-injured 23 year old helmetless/insuranceless idiots who thought they were invincible. But mostly it's cuz I love my friends' brains and I don't want them smushed. I can argue with them only so far; I want a law that makes them (and my friends' friends and families that I can't talk to directly) take safety seriously.

Even if it's not fully enforced, a mandatory helmet law will get more people to put one on. I remember when seatbelts became mandatory - lots of people grumbled, but now pretty much everyone wears one. Helmet wearing is one behaviour I'm willing to have legislated.

And, for anyone who wants to know the current law in their area:

http://www.helmets.org/mandator.htm