Most cyclists don't wear helmets to protect themselves from cars. Most of us wear helmets to protect us from the ground. I've biffed 6 or 7 helmets and all of them were due to impacts following a fall. In a collision with a car, the helmet won't usually do much in the primary impact (our heads are usually higher than the car) but it will help in the secondary impact when the cyclist hits the ground.

On a secondary note: If Stossel rides to work as much as he says, why doesn't he raise his saddle! If I rode anywhere with my saddle that low, my knees would kill me He'd also get a whole lot more respect from motorists if he'd ride predictably.