WASHINGTON (CNNMoney) -- Little is known about key details that led Standard & Poor's to downgrade U.S. debt late Friday, despite its outsized repurcussions. While the move knocking U.S. debt down a notch from the lofty AAA rating has exacerbated an already skittish stock market and drawn criticism from the White House, key details are a mystery. S&P doesn't say who, exactly, made the decision at the company; what kind of weight they gave U.S. politics versus ability to pay; or to what extent they felt pressured to downgrade the United States in response to criticism of its downgrades of...