I'm impressed this thread is still open! (I haven't read many of the posts)

Riding without a helmet is wonderful, I do it often. But on my work commute were I'm on high speed roads with plenty of motor traffic I always wear one... not for protection in case of a fall, but because I find it to be a convenient place to mount my mirror, reflective tape, and sometimes a tail light. THOSE items I do feel actually help to prevent a wreck!