Wow, as a relative newbie I didn't realise helmets were such a dramatic subject! FWIW I tend not to wear a helmet if I'm just nipping to the shops or pub etc on the basket tank bike but I always wear a helmet on the roadie - think its habit mainly, compulsory for sportive and club rides and now feels odd to not be wearing one! I rode horses for years where its just automatic, however on occasion I've jumped on the odd horse without a hat if I'm teaching someone and need to show them, or bringing a horse in/out from the field etc. I'd never really thought about why I always wear one on the roadie but never the tank, maybe it's because of the speeds involved? Last time I fell off I was going down a hill, round a corner, too fast, hit some gravel and the bike slid out from under me and I hit the deck. First thing my mother said to me when I told her later that week, "I hope you were wearing a helmet!" - which I was, however not on my hip, knee or elbow - the parts which made contact with the ground! Obviously I'm aware that different factors in different falls/accidents/collisions etc will produce different areas of contact with different materials. I've not done the research in to the topic myself but I find the whole argument that helmets are a myth put about by cycling shops to rob us of our hard earned all seems a bit paranoid! Anyhoo I've never looked at another cyclist and consciously noticed whether they were wearing a helmet or not - I'm normally concentrating on trying to look cool and not like I'm at all struggling whilst they coast easily by. . .