The problem with this debate is that so much evidence is anecdotal.

People have an accident, the helmet breaks and they get light concussion. Conclusion - the helmet saved their life.
I had an accident a while ago, got knocked out, had mild concussion and wasn't wearing a helmet. Conclusion - I should have worn a helmet.
But neither of these situations prove anything. The helmet may have made little difference in the first or second examples.

I think the problem that these anti-helmet pages have is that although you can argue that helmets don't do much to protect you (my personal belief), it is pretty hard to prove that they cause injuries (that neck torsion thing seems a bit far fetched).

So the conclusion is that you should wear one on the balance of probablilities. I still don't cos i am a fashion victim.