I have the impression that some of the big hedge funds and banks (that also pay S&P for ratings) knew about this downgrade at least since monday aug 1st. That selloff after august 1st. came after the US increased the debt level. It more or less came as a sudden surprise. I almost think some big banks knew about the downgrade and went short like mad. Today they know margin calls come in and they cover their shorts. Really feels that way. Any opinions ?