t r u t h o u t - NSA's Vast Spying Yields Few Suspects: "Valuable information remains valuable even if it comes from one in a thousand intercepts. But government officials and lawyers said the ratio of success to failure matters greatly when eavesdropping subjects are Americans or U.S. visitors with constitutional protection. The minimum legal definition of probable cause, said a government official who has studied the program closely, is that evidence used to support eavesdropping ought to turn out to be 'right for one out of every two guys at least.' Those who devised the surveillance plan, the official said, 'knew they could never meet that standard - that's why they didn't go through' the court that supervises the Foreign Intelligence Surveillance Act, or FISA."

(Via t r u t h o u t.)