I work(ed) for a NEUROC/WEROC team, and I think the biggest problem here is people are not tightening down thier seatbelts enough.
I see this from a paramedic point of view, as well as a buggy builder point of view.
From what i have heard, (friends at the event), he knocked himself out hitting his head on the steering wheel, and in the slow motion, you can see him flailing around in there alot. If you have ever looked in a comp buggy, your seat belts need to be very loose to hit your head on the steering wheel... its a long ways away.
You have four point belts for a reason... make them tight!
Race cars are different because you dont have to look all around like you do in a buggy, but loose belts are not worth the seeing if they are going to cause injury, IMHO.
I'll get off of my soapbox, it has just been a rather hotly contested issue around the shop.