I was just thinking - don't get me wrong - but is there any way to know whether if the surveillance actually protected any terrorist attacks, and if yes, how much? I think it is theoretically possible that it helped to prevent many attacks, but government could not announce it because that would reveal the whole network. It would be best if somebody would leak some documents that would show the terrorist attack being prevented. That would probably be the first leak that revealed not the crimes of the government, but actually good work, that was supposed to stay a secret.