This is not intended to be a 'for or against'.
As gembo has said elsewhere "What I note is that people are biased and therefore look for evidence which suits them [when I say people I mean me and you and everyone else]"
I hope helmets will always be a personal choice. Most people wear them when riding off-road, because they perceive the dangers to be greater than riding on road (obviously many people wear helmets on-road too).
There are people whose quality of life is better because they were wearing a helmet when they came off their bike. There are people who are/aren't alive because they were/weren't wearing seat belts (etc.)
My problem with the 'helmet debate' is the polarisation/'certainties' - usually based on statistics which are not easy to absolutely quantify/verify.
E.g. life expectancy increase due to regular exercise (e.g. cycling) v death/injury due to not wearing helmets. This is periodically debated in the BMJ and often refers to the results of Australian helmet compulsion.
There are parents who somehow imagine that if their child wears a helmet they are 'safe' - irrespective of a) whether it fits properly, b) the road sense of the child c) the state of their bike...
DEBATE!