"The US losing its AAA rating matters. It is a very loud statement that there has been an appreciable increase in the risk - which might still be tiny, but it exists - that the US might one day struggle to pay back all it owes. Another important certainty in the world of finance has gone.
Of course many will argue - and already have - that the record of ratings agencies such as Standard & Poor’s of getting these things right in recent years has been lamentably poor. Think of all the subprime CDO products rated AAA by S&P that turned out to be garbage.
But S&P, Moody’s and Fitch (and particularly the first two) still have a privileged official position in the world of finance: they determine what collateral can be taken by central banks from commercial banks, when those central banks lend to commercial banks."
