The credit rating agency Moody's slashed the ratings of 15 of the world's biggest banks, including most of the big guys here in the U.S.

Global markets are down about a percent this morning after the rating agency Moody's downgraded the credit ratings of 15 of the largest banks in the world. Among them, European institutions — but also big American banks like JP Morgan Chase and Bank of America.

U.S. banks are getting a harsh reception from ratings firms, regulators and even investors. Do they deserve the abuse?