In all fairness, Palin's problem wasn't that she didn't know the answer. Her problem was that there was no answer. McCain was going around the country lying about how he had supported regulation of the financial markets which could have prevented the current collapse. He hadn't. As Couric pointed out, McCain had consistently voted with his fellow Republicans to repeal every manner of regulation. Now that that policy has led to disaster he was trying to lie his way out of it. That wasn't Palin's fault. If Couric had asked McCain the same question he couldn't have answered it either.
Admittedly, if McCain had ever voted for rather than against a regulation, there is no chance Sarah Palin would have known about it.
What I think was the worst thing I heard about Palin was not that she was a moron. There have been plenty of those in high office. She is no stupider than Dan Quayle, for instance. Nor that she was a hypocrite and a liar as shown in the Youtube video here:
There have been no end of those in high office in my lifetime too. The worst thing I heard about her was that her staffers had urged her to prepare for the interview and she had refused. Repeatedly. Which is why she got clobbered in interview after interview.
George W. Bush has never been accused of being any great intellect. But he seems humble enough to realize it. Nor was Ronald Reagan any mental giant. But he had a formidable work ethic and was always so well-briefed that he was bulletproof even under hostile press questioning.
Palin is both ignorant and a moron, and simultaneously too cocksure to realize her limitations. That makes her truly dangerous.