I always encourage people to wear helmets and I never ride without one but in terms of safety, good cycle paths and cycling friendly roads are probably more important.  

Those stats are really interesting though. It's quite a large drop. I must say I think they have stretched things a bit in their list of disadvantages of wearing a helmet and provide no evidence for many of them.

And hello?
The Case Against Bicycle Helmets and Legislation

The Holy Bible provides an early example of allowing for personal choice with David choosing not to wear either a helmet or armour when fighting Goliath. In that case Goliath's helmet failed to protect.