CNN.com - Experts: A variety of intelligence factors may have played a role - September 16, 2001

" "The intelligence community was completely caught off-guard then," he said. "And the CIA and the intelligence community was created by the 1947 National Security Act to prevent future such surprises, which raises real questions about what has happened in the last 50 years." "

The problem with institutions like CIA is that we don't know how many "secret" attacks they have prevented in the last 50 years. They might have been very efficient - an efficiency rate of 99% wouldn't be bad... although tragic to the victims of the last 1%.