I don't wear a helmet because I don't like the feel of the strap under my chin. I'm a careful rider and never go faster than I feel the conditions warrant, but I have three chips in my windshield from rocks being shot out from the tires of other cars, and I've always wondered what the odds were of one of them hitting me square on the noggin while biking. I worry more about that than I do crashing (and this has been a pretty hard winter on the roads - lots of potholes and loose concrete).