I'll add that recent points about costs for young vs. old, use of benefits vs. what's paid in all highlight the problems with viewing health care need as something that should be insured against.
It seems to me that folks of all ages don't perceive value in their health spending the way they do, say, liability insurance or auto insurance. That is, something you pay for that you hope you wan't ever need to use. Sure, no one wants to get sick -- but health care also keeps you healthy, bear children, etc -- you should WANT to spend some money on it. However, as we all know, the market is not efficient and demand is not elastic.
Once everyone's in the pool, it's almost like the pool disappears.