Originally Posted by Geordi Laforge

I believe I read that most head trauma from bicycle accidents happens on the forehead, so dont wear your helmet high - make sure it covers your forehead or isnt so loose that it can easily be forced upward exposing your forehead.

The problem with some helmets that have large extruding vents on the back is neck injuries because your body might roll one way but be stopped by the helmet. the neck can get twisted.

http://www.helmets.org/