Scientific American put up a nice layman's medical summary of the issues here:
http://www.sciam.com/article.cfm?id=...die-richardson
If you have an aneurysm or a weakened vessel, it may not take much? Reading all this ski resort fatality stuff lately (and also taking a WFA course and learning how I and the patrollers didn't take nearly enough precaution afterwards) has gotten me spooked after my crash 2 weeks ago - I feel like a lucky SOB.