I think the thing to keep in mind is that the blunt impact head injury is the result of the fall distance from how high your head is from the object (usually the ground) it strikes. It's not at all normal the speed at what you are traveling into something. Like a tree, ie Sonny Bono.
Like JJ said, wear a helmet unless your a donor. Also, remember that a $10 helmet = $10 head. I have a friend that is still "alive", that had blunt force trauma from a fall on a motorcycle. It slide out from under him at about 5 mph. His head hit a curb, and he is nothing like what he used to be. Nobody home, violent, and does not know who he is...
Finally, thanks for your condolences guys. I hope you two guys (JJ and CB) get to live alot longer. I'd certainly miss your input if you didn't come back here.