I would rather consider the worst case scenario of a given set of intelligence and overshoot than underestimate and have it come back to bite me in the ass.

Lets say the US intelligence community played down the evidence and Bush decided not to go to war. Saddam gives a terrorist one of his biological weapons that we downplayed and it is used agains the US say as a dirty bomb in Los Angeles. Do you not think Michael Moore would be all up in arms that Bush did nothing to prevent this? I certainly would be.

If our intelligence is to be flawd I would much rather it be an overstatement than an understatement.