Where are the uninsured?

Megan McArdle at The Atlantic has noticed something very interesting: only about 18,000 people have signed up for the high-risk insurance pools set up by Obamacare. That's pretty incredible, considering these pools cover those who were the biggest justifications for the legislation -- those with pre-existing conditions that the evil insurance companies downright hate. McArdle explains:

I've predicted that lots of parts of Obamacare will not work the way they're expected to.  But here's one I wouldn't have predicted: the high-risk pools, which were meant to tide people over until 2013, have signed up just 18,000 people as of March.

There were supposed to be millions of people who were uninsurable because of pre-existing conditions.  We heard lengthy testimony about their terrible plight.  I don't think it's too strong to say that this fear--that you could get sick and no one would insure you, that's right, you, Mr. & Mrs. Middle-Class Voter--was one of the main reasons offered for the health care overhaul.  It was estimated by Medicare's Chief Actuary that around 400,000 would sign up (the CBO estimated 200,000, but only because they assumed that HHS would use its authority to limit enrollment in order to stay within the $5 billion budgeted for the program).  So where are all the uninsurable people?

The explanations so far offered don't sound very convincing to me.  Suzy Khimm channels Nancy Pelosi to suggest that the political controversy over Obamacare has somehow prevented people from finding out about high-risk pools.  I could certainly see how that would account for fewer-than-expected signups . . . but a 95% reduction?  It sort of strains credulity to say that only 18,000 uninsurable people in the whole country are aware that the pools exist--at least, if you believe that all the rest of the uninsurable people care about getting health insurance.