>>>The study in your link does not answer (that I saw) the question I had: how common are bicycle accidents that cause head injuries in the first place? My guess / assumption is not very. No question that if it should happen you would be better off wearing a helmet. I just don't think the chances of it happening are enough to worry about.
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>>Here's some more data: http://www.helmets.org/stats.htm
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>>Seems to me that helmets are an easy, inexpensive way to save lives and prevent injuries. (Kind of like seat belts.) Pardon the expression, but it's a no-brainer to me.
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>To you. As I said to Doug, reasonable people can disagree.

Unfortunately I think this is an area where the well meaning safety lobby have over done it. By making cycling sound like a high risk activity they have put many people off it with a knock on affect on general fitness. Holland has one of the higher cycling rates in the world and very few people wear helmets.
The head is certainly one of our most vulnerable parts. The designer should have stuck the brain where the heart is. You could make the helmet argument for many activities that involve risk of falling.