Paul Krugman points out that quite a few sick people fall victim to rescission, the retroactive cancelling of health insurance.
From his blog:
The industry would have you believe that it’s a minor issue, because only a small fraction of the insured experience rescissions in any given year. But as the post points out, a small fraction of the insured experience a large share of medical expenses — and you can bet that rescissions are concentrated on the people with big medical bills. So half a percent, if that’s really true, is a large fraction of people who really need coverage.
I’d add that rescissions must be concentrated in the individual insurance market, since group coverage is, by law, not contingent on medical history. And the individual market is a small fraction of the total; again, this must mean that the phenomenon of insurers pulling your coverage when you get sick must be quite important indeed.
Paul Ryan's buddies atAssurant know all about rescission.