They've got muck; we've got rakes. TPM Muckraker

"The Pizza Hut Leads"

[F]or every real lead with a plausible terror connection, there were many others that washed out, the trail gone dead, the connection uncertain. NSA officials saw their surveillance and data-mining work as vital to stopping another attack, but at the FBI, officials complained privately that they were forced to chase many hundreds of NSA-generated leads that inevitably arrived at dead ends. The “Pizza Hut leads,” FBI officials began calling them derisively, because in the six-degrees-of-separation world of tracing who had called whom and whom that person had called and whom those people had called, the NSA leads often seemed to wind up with the pizza delivery man.

For all its useless leads, the data mining part of the operation was more controversial within the Justice Department, as Comey's testimony last summer made clear. All of this might have gone on indefinitely if Jack Goldsmith had not been tapped to lead the Justice Department's Office of Legal Counsel in 2003. Backed by Comey, his concerns about the program's legality finally pushed the Department into conflict with the administration over the program. You know that story -- the showdown between Department officials and Alberto Gonzales and Andy Card in John Ashcroft's hospital room.

The president backed down and told the Justice Department to make the necessary changes to the program. What those changes are, we still don't know exactly. But Lichtblau gives a good idea of the contours:

A detailed checklist containing some twenty items would be developed to determine how exactly the NSA went about determining who was a suspected member of al Qaeda when it started eavesdropping. An audit of past wiretaps would be conducted, with the Justice Department’s active involvement.... And most critically, several specific aspects of the program would be shut down altogether. What exactly the NSA shut down in order to keep the program alive remains unclear even today, but according to intelligence officials, it appears to involve several distinct and technical aspects of the operations that relied on the use of data-mining to trace communications patterns across U.S. borders, elements that officials at the Justice Department thought were particularly problematic in a program already rife with legal complications. “Imagine you’re doing ten things one day, and the next day you’re only doing eight of them,” one official said. “That’s basically what happened here.”