Someone posted an updated study a while back, with figures indicating that the less serious an injury is, the better helmets do with protection. While that might be stating the obvious, the numbers were interesting, and the study came to the conclusion that helmets helped mitigate injury even in half of serious injuries, a majority of moderate injuries, and most light injuries.

That said, if all a helmet helps with is superficial cuts, contusions, and abrasion injury, in the very rare instance of a crash with helmet contact, that's reason enough for me to wear one...