Yglesias weighs in:
...this sorry tale further illustrates some of the problems with torture. You can’t very well say “well, we brutally tortured this guy dozens of times and it was all basically pointless.” Having ordered the torture, you now have a bunch of torturers, orderers of torture, etc. invested in overstating the utility of torture. And of course if torture worked so well on the one guy, why not torture some more people? Indeed, the whole rotten idea of torturing KSM seems to have stemmed in part form an unwillingness to admit that torturing Abu Zubaydah was pointless.
And, worse, all kinds of legitimate intelligence work aimed at trying to understand al-Qaeda’s structure were compromised by the fact that some people now had a strong incentive to keep overstating Zubaydah’s significance.