The criterion of "will surveillance and secrecy be reduced as a result" is the only relevant one. Naturally we can't know results in advance for certain, and that means we can't grade actions like Snowden's in advance either. We do the best we can, but it's still legitimate to point out that the true impact of Snowden's actions is not yet known, when the discussion is about how much you expect to benefit from similar actions taken by others in the future.