It only occurred to me quite recently that Mitt's inclination to bike without a helmet may stem from fear of The Dukakis Effect. Everyone looks like an idiot in an oversized helmet. A political candidate can't afford to be photographed looking like an idiot. Notice that in Romney's ad centering on his athletic vitality, he's running. Running is a more macho activity than cycling and avoids the helmet question entirely.
Maybe those of you who aren't in early-primary states haven't seen Mitt's ads yet. You'll get your chance.
The dork factor still plagues bike helmet wearers. I may use one, but I will be the first to admit that no one looks punk or tough or cool with a salad bowl on their head. One customer complained that the pointy back end of the average helmet "made him look like a woodpecker." It also seems like tremendous overkill when running short errands. But accidents are by nature unpredictable. Your odds may improve in some ways if you are not exposed to a situation for as long, but the other risk factors still apply. Gravity is as strong. Other road users are as unpredictable.
I miss the care-free days of cotton caps in summer and woolen beanies in winter. I still have my cool-looking Italian wool winter hat. And I don't miss the hot, heavy, clunky-looking Bell Biker. I switched to the somewhat more acceptable (but probably less effective) Brancale for the last couple of years of my licensed "career." In 1988, Tim Blumenthal called it a "Fred Hat." Soon after that I was sucked back into the bike business and could start buying more up-to-date brain covers.
I used the Brancale for whitewater and climbing. Climbing and paddling helmets accept the dork factor without putting up even a token resistance.
Those who would lead this land of the free end up being some of the least free. They have to worry at all times what the public will think of them, regardless of whether it is fair. The rest of us can look like whatever kind of idiot we choose.