Although the issue is beat to death here are my feelings on wearing a helmet. I wear one all the time, I don't believe it will be much help in a serious accident, it may prevent scratches if I were to fall over or crash at a very slow speed. I wear one for two reasons, the least important being, the helmet has air tunnels that actually cool my head, the most important reason is the children. When I'm riding on my flashy, high tech bike, wearing a good fitting jersey, shorts and shoes. I look like a cyclist, The children in their yards and along the roads see me and notice me, they ride bicycles and tricycles. They have undeveloped bone structure that will benifit from the protection of a helmet if they were to tople over. I have been told a number of times by parents that it's easier to explain to a child that wearing a helmet is benefitial and the right thing to do and is part of riding a bike. I ride responsibly and try to set an example for the up and comming cyclist to wear the proper gear, ride responsibly, enjoy the sport and live to tell about it.
Oh and it keeps the sun off the bald spot.