I think it's interesting that if you are a professional policymaker or pundit, you face approximately the same amount of accountability as anyone else or, arguably, less.
In most fields some mistakes are tolerated. You might get fired for making a particularly bad mistake, but chances are you can go out and get another job at another company in the same industry doing mostly the same thing. Some professions are particularly mistake tolerant, (see: publishing, professional psychic, blogger), and some are relatively mistake-intolerant, such as the medical, legal, and civil engineering industries. In mistake-intolerant fields, you usually have a system of accreditation and an organization that's in charge of enforcing industry standards. If you mess up badly, or if you screw with this organization, you will not be able to practice your profession. The AMA, the Bar Association, etc..
The political world has some aspects of tolerance, and some of intolerance. The media and the electorate are the enforcing institutions for elected officials. Get caught having the wrong sex and your career as a politician is over. Note that the political world's sensitivity to personal scandal is practically unique--in most other professions you can move on with only some minor embarrassment. In addition to the tabloid press, elected officials face elections, which ostensibly hold them responsible for decisions made and punish mistakes made. Losing an election is often career-ending for politicians, BUT policymakers and pundits are not all politicians, and retired politicians can move into this other class of non-elected policy professionals.
There seems to be no broad mechanism in place for holding policymakers or pundits responsible for errors in judgment. There is no professional association to ensure high standards. The press do not make a habit of checking and revealing track records, and there are no elections for these positions. Therefore, without a quality enforcement mechanism, the field of policy making and punditry are mistake tolerant. And that is why the people who made all the mistakes five years ago are still respected, professional pontificators. Wacky, eh?