[grourk]

S&P and Moody's don't exactly employ an "army of experts" either. It's a few analysts making a rather subjective judgment and voting. (Literally, a few).

And the investors who are actually buying US debt don't rely on ratings agencies to give them guidance, and do in fact have expertise in-house to evaluate these things.

As has been mentioned elsewhere on this thread, institutional investors don't treat US bonds like any other, subject to triggers and rules like AAA-only. It's an exceptional case that is treated differently than the others, and one rating agency's opinion is not going to make as big an impact as people seem to think.

It comes down to this: where else would they put their money?