I absolutely think there is a false sense of security. There was an article years ago in the WSJ proposing banning the helmet or going back to leather helmets as a way to limit head injuries.
On a personal note I have found a difference in the way I ski when I have a helmet on as opposed to a regular winter hat. You tend to "feel" more invincible, take more risks, realize that if you do get out of control you have a helmet to protect your head.