Ace has done some phenomenal work piecing together a very probable timeline leading to the raid on Abottobad.
1. 2003: Enhanced Interrogation of Khalid Sheikh Mohammad Results in the Nom De Guerre of bin Ladin's Courier.
Enhanced interrogation techniques did not, however, produce the real name of the courier -- at least not this earlier; it seems to have happened later.
This is giving the pansy liberals and McCain "We're better than this" types the pretext to deny the usefulness of such techniques:“They waterboarded KSM (Khaled Sheikh Mohammed) 183 times and he still didn’t give the guy up,” said one former U.S. counterterrorism official who asked not to be identified. “Come on. And you want to tell me that enhanced interrogation techniques worked?"
Yes, because he did give the guy up: he gave you the nom de guerre.
Further, I can think of a rather obvious possibility as to why he didn't give the real name up: He never knew it. Bin Ladin told him the codename; why would KSM need to know more than that? The most important practice in any covert organization is compartmentalization of information -- the famous "need to know."
Go and read through the whole piece and you will be light years ahead of most folks as far as understanding how this came together.