Some Wall Street analysts question Moody's sunny outlook, noting that the agency also seemed confident earlier this month that a government shutdown either would not occur or would be short-lived. They say the credit gurus appear to have been taken by surprise by the intensity and length of the latest impasse, raising the possibility that global markets could be shaken violently by a sudden and unexpected downgrade by Moody's, S&P or Fitch once they are jolted back to reality.