Personally, I don't think anyone should HAVE to wear a helmet. At the very least any operator of any vehicle should have the choice. I feel there has been a 'safety-slide' since I was a kid. All of this is what makes kids soft nowadays. Bumps and bruises are part of life. I don't doubt for a second people get hurt on bikes (heck Dan from Iride almost got paralyzed), but for the average joe shmoe riding the cruiser, we shouldn't have to.
Riding a bike comes with what a lawyer friend called assumed risk. To argue that everyone on a bike needs a helmet is ridiculous. By the rationale that they should wear one, the logical extension would be knee pads since your knees would quite often hit the ground first. What would next if you fall? Hmm.. well let's see, elbow pads and gloves to protect your hands from road rash as you slide to a stop. Then to extend this further all bicycles will have training wheels (soon called 'safety wheels') on them. We certainly can't have these dangerous things on the road (or safely paved trail) with only two wheels, what if you lost your balance?
In fact in a few years I foresee a crusade to outlaw bicycles. they will say that they are just to risky to be ridden since there just can't be a way to mount an airbag on them. This outlawing will come no doubt after the passing of the bicycle seat belt act fails to save enough lives. I mean what legislator wants to be seen as taking a stand against something that puts children in harms way? Bicycles will go the way of the easy to light Bic lighter and Lawn Darts. Ejoy them while you can.
....sorry, I had a stream of thought going there. Had to get it out.