I have to agree. The NSA may or may not have stopped any attacks with this snooping. They can of course point to attacks they claim to have stopped, but sadly we can't verify any of that. Instead we can point to the Boston Marathon Bombings where the US Government was informed by other countries to watch out for these guys and we still did nothing.
We also have the Fort Hood shooting. Where any Army person was using army computers to contact terrorists and went on to shoot up an army base. Where was the NSA there?
"Days after the shooting, reports in the media revealed that a Joint Terrorism Task Force had been aware of e-mail communications between Hasan and the Yemen-based cleric Anwar al-Awlaki, who had been monitored by the NSA as a security threat, and that Hasan's colleagues had been aware of his increasing radicalization for several years. The failure to prevent the shootings led the Defense Department and the FBI to commission investigations, and for Congress to hold hearings."