I don't see why this should be controversial: protecting your head is the best thing you can do to turn head injuries into non-head injuries. Pointing only to fatalities, as the virus-ridden link that Wendy provided, misses the vast majority of accidents. Of course a helmet is useless in an accident that would otherwise kill you anyway. Duh?
An excellent place to look to information about this stuff is battlefield injuries: the rise of, and increasing sophistication of, helmets by soldiers has completely changed the nature of the number and scope of injuries in battle over the last century.
Other people -- like construction workers and fire fighters -- don't wear helmets because they are tools; they wear them because the risk of head injury in what they do is significant, and they work. Head injuries are typically the most avoidable injury there is.
/jordan