One stat they forgot to mention is how, when speeding down a single track, a branch might go through the vents twisting your head around and braking your neck.
I have hit my head many times with out and with a helmet. I much prefer to do it with a helmet now
I always wear a helmet when I ride these days. It is not the fear of death that I wear one but the pain of a serious head injury that does not kill me.
About the manditory helmet law. For the younger riders it is a good idea but the problem I see is not that they do not wear the helmet but they wear it improperly. Most of the young kids around here that wear helmets never buckle them. I always see them crashing and most of the time the helmet is off their head before they even hit the ground.