What is it exactly that Snowden did that so many Americans consider to be bad? I think many Americans assumed such practices likely existed, and believed them

What is it exactly that Snowden did that so many Americans consider to be bad? I think many Americans assumed such practices likely existed, and believed them to be useful tools against terrorists and criminals. They believe that Snowden has reduced the effectiveness of these tools. For example, most people know we have spies. But I think these same people would be upset if someone said, "We have two spies in Pakistan working with this group. And a common technique for this group is to infiltrate via this mosque, where we have several spies, etc...". While this isn't a list of the names of the spies, people would probably believe at even this high level of specificity that the effectiveness of their intelligence gathering would be reduced. I personally have mixed feelings about it. I do think that to the extent that the gov't is doing something illegal, whisteblowers should be empowered to stop it. On the other hand, I think the capability of our intelligence gathering should be as secret as possible. It's not just what can they do that should be secret, but what they can't do. Some people think that terrorists are hyper-aware and practice perfect security. I suspect that they make a lot of mistakes and have a lot of assumptions. Is Snowden a hero? I think history will decide this question. If we see a freer US as a result then I think he may likely be viewed that way in the future. If instead it turns out that our intelligence agencies were practicing disciplined filtering and thwarting attacks, and in the future we're outmaneuvered due to these leaks then I think history will view him in a different light.