The US has not had its fiscal house in order for nearly a decade. That entire time Moodys left the US rating at Triple A. When there are finally discussions to lower the deficit Moodys comes in and warns of a downgrade. Talk about closing the barn door after the horses have left.
This is what the ratings agencies have done consistently. Instead of acting as a counter cyclical force, they act in a procyclical manner. During good times they encourage people to make bad loans and during bad times they cause borrowing markets to freeze. This exacerbates the cycle to the upside and downside when they are supposed to be doing the opposite.
On a separate note, I would like to thank them for the buying opportunity last night.