> You insure yourself against exceptional things.

This isn't strictly true. We insure against the unexceptional as well. With regards to your specific example, I think refunding the flu shot is perfectly reasonable and an elegant solution to solving the social problem of getting people to be healthy. We all pay higher premiums but only those that actually do the preventative stuff get any benefit. Put another way, if health care plans were $1/month cheaper and the cost of the flu vaccine was $12, I'm pretty sure we'd see our already lackluster yearly vaccination rate plummet.