Why would telling the American people how much you are using the powers given by the people threaten your protection of the people? If Obama said how many drone attacks have been carried out, that wouldnt help a terrorist evade Drones. The idea that informing America of the amount of wiretapping that goes on would threaten the NSA's operations is seriously wrong. Unless the NSA is counting lack of oversight as an operation. Which is wrong.
Well, if you know there's 2 drone strikes a year, you wouldn't worry about a drone strike as much. But if there's 100,000 a year, suddenly there's a whole different problem back home defending that.
But what makes this a stupid defense is they aren't asking to make the numbers public, it's about making some top level data available to congressmen, which I would think should be indefensible.