The same could be said for just about every other participant in banking, real estate, government financing, etc...including individuals who bought houses at the top of the market. It ignores the ability to learn from mistakes. The point here is that the ratings agencies are going to be much more careful handing out AAA ratings in future, BECAUSE they messed up. It's exactly the collective short-term memory you refer to, in action.

An AAA rating should be conferred on an entity that is riskless. The recent debt debacle is very likely to be repeated in the near future. These are not the actions of a riskless entity.