Comedian Jerry Seinfeld onced mused about the wisdom of wearing a helmet when sky-diving. He concluded that if your parachute failed and you hit the ground at terminal velocity, you would (for all practical purposes) no longer be wearing the helmet. Rather, the helmet would be wearing you, saving it from serious injury/damage at impact.
With that said, three cheers for the flying-squirrel men of New Zealand! And remember kids, if you try this at home, always wear a helmet. (Note: do not try the somersaults on your first day. You see, we build to that...)