Good post to the above... I do agree with what he said. I almost want to repost it as the second post, every time someone starts acting like we bought into a pyramid scheme by wearing helmets.

The data is just not there. I would think that if you are riding with groups or racing a helmet would be even more beneficial, which might have an effect on roadies more. It seems like packs of riders are more likely to go tumbling and hit their heads on other helmets/bikes/the ground than just getting smushed by a car.

That's just me theorizing, though.