Not sure if it has been posted prior but here is a link with lots of statistics about helmets and cycling from various sources.

http://www.bhsi.org/stats.htm

Riding without a helmet is on the same level as fixers who ride without brakes. It is all about the person making a "statement" about their prowess at cycling or their individuality or anti-establishment or whatever... If you want to crush your skull it’s your business up to the point where your stupidity begins to affect other people in any way. Show proof that you have enough cash in the bank that will cover your injuries and you can ride naked for all I care. However, if you’re dependent on the rest of us to take care of you after you have a fall, I have a problem with you not taking reasonable precautions. Wearing a helmet is not, in my estimation, unreasonable.

Hopefully you understand enough about economics to understand that all costs for goods and services are ultimately paid by the consumers. A lot of the public is under the mistaken belief that the insurance companies pay for care. They don't. The policy holders of the insurance companies pay for care. That's me and the rest of us who have any kind of insurance. So, you do not pay your costs in the hospital alone. That is why the rest of us have some legitimacy in being upset by those of you making a statement at our risk.