Helmets.........?
[pulls soap box to speaker's corner...and steps up]
People ride bikes with helmets, and without.
I used to always ride to work with mine, then I fitted a mirror which has increased my (feeling of) safety immensely. I no longer ride to work with a helmet.
When out on my racer/roadie (call it what you will) I wear my helmet. The roads round these parts aren't the best, and the tyres pick up punctures like John Terry picks up other people's (ex) girlfriends. Also, the tyres are a lot slimmer, and as I ride on gritty lanes and back roads, as well as on damp roads, road traction in corners is reduced. The speeds attained on my racer are higher than my commuter/tourer too, and I am more likely to hurtle down a hill to keep up my 'average', whereas on my tourer/commuter I am more interested in looking around and enjoying the countryside.
Interestingly, my racer doesn't have a mirror.
Helmets are a choice item.
I choose when and when not to wear one, depending on the riding style. I think people (on both sides of the helmet debate) ought to be more truthful about why they do wear one, and people a little more inward looking as to why they don't.
I use a common sense approach that works for me.