At least in California, the legislation was put into effect soely because of the state footing the healthcare bills for those who are dependant on state care for the many expensive-to-treat and preventable head injuries. Ideally, if the state takes care of your butt (or your head, or any combination of the two), then I'd say they have a right to tell you you have to wear a helmet.
Obviously though, that'd be impossible to enforce.
I guess the next best thing would be for the insurance companies to do the ruthless enforcement--that's their specialty, after all.
It's hard, because I do believe that helmet laws save and improve lives in general, but it's easy to see how this line of thought could be abused by the government. It's also easy to see how the general public could also take this arguement to rediculous extremes.
Edited to add: I do like the idea of the mandatory organ donorship if nothing else but to make a point, but I'm sure that would inflame people who don't want the gov't to impose *that* either.
For the record, I'm highly in favor of organ donorship. By force, if needed!