As a keen cyclist with children, I had always been in favour of the New Zealand law making it compulsory to wear a bicycle helmet. However, the outcome of that law is apparently not what one might have intuitively expected - according to a 2012 report from the NZ Medical Journal. I'd not seen it before. Very interesting statistical analysis.
Evaluation of New Zealand’s bicycle helmet law - New Zealand Medical Journal
Seems like a good article
I remember reading a report in some Sunday paper a good few years back that claimed that wearing a helmet while cycling led to drivers taking less care around cyclists, which in turn led to more accidents and fatalities.
(Sorry, no links. The statistics for that article came from France IIRC, & FWIW.)
I cycle regularly in the summer. I've found that if I cycle well, i.e. keep a very straight line, some drivers will pass dangerously close to me. So I tend to weave slightly to try and keep them more aware, and wary, of me. Not ideal, but I'm still here :-/