No evidence Snowden leaks caused any harm

That's right, no evidence has been provided to that effect. Repeat, none. There's plenty of accusations and hypothetical scenarios, but to date there is no evidence. The government hides behind the specious rationalization that they cannot reveal such evidence for it would further endanger lives. That is not evidence but a smokescreen. In another case of purported leaks causing damage, nothing presented in open court during Chelsea Manning's trial supported that allegation. Again nothing, no evidence. Such claims should be investigated by Congress, the GAO, the IG and determine what harm if any has happened. And that should be weighed by the good such whistle blowing brings.