Nova has made a documentary about the NSA called, 'The Spy Factory' which was very informative and interesting. According to heads of both departments, both the NSA and the FBI had advanced intelligence regarding the September 11 attacks, but for some reason didn't share it with each other. The claim being that had they done so the attack might have been prevented. Allegedly in January of 2001 all of the cryptographic supercomputers in the NSA suddenly shut down (Nova did not give an explanation why) and were unable to gather intel for around 5 days which just happened to be a crucial window in which the terrorists inside the U.S. were communicating with their headquarters overseas and receiving instructions. The timing here is incredible, isn't it?
A few years after the September 11th attacks President Bush secretly passed a law allowing the NSA to spy on American citizens which includes listening to ANYONE'S phone conversations, intercepting emails, IM's and faxes all in the name of national security.
It's interesting to me that an agency with an annual budget of around $50 billion, staffs 35,000 employees and just happens to be the most sophisticated collection of the worlds greatest mathematicians, linguists and computer scientists by it's own admission happened to have critical intel fall through the cracks. Hmmm.