According to the Wall Street Journal, there is some evidence that the football helmet, no matter how advanced, may cause more head trauma than it prevents.
The gist of it is a mutually assured destruction kind of thing: the helmet leads to a sense of invulnerability that in turn leads to dangerous tackling techniques whereas hatless players avoid dangerous contact to save their own brains. Australian Rules Football is discussed as a comparison, and Dhani Jones is quoted.
My two cents: I had two concussions playing football, one with a helmet, one without. Neither was enjoyable.
Discuss, oh concussed masses.