Do I have evidence? No. But I am not a prosecutor or a cop. So, when I say such stuff, I am offering my opinions. Based on what? On inference. How so?
Well, a guy seeks to penetrate American intelligence agencies and their computer systems to download secret stuff. Then he flees to countries that are adversaries of the United States. He is welcomed and seems to be employed these days by Russia. The decisions to allow Snowden into Russia and hang out must have been made at the very highest levels--by Putin. Either Putin is a huge fan of complete transparency and the freedom to engage in dissent or he has other reasons for supporting Snowden. Is Pultin altruistic? Um, no. Is he a fan of transparency? Not in his country.
In the good old days of the Cold War, there would be very few questions about what is going on. Here, because Snowden blew the whistle on the National Security Agency's domestic spying, he is seen as a whistleblower. And I would agree if that is all he did. But he went further than that, releasing a bunch of information about American intelligence and cyber operations that really did not need to be released.
It kind of parallels one of my rules of writing--just because you learn something does not mean you should include it in your article/chapter/dissertation. If you want to point out that the NSA has been doing illegal stuff in the US, that does not mean you need to release information that might just be helpful to other countries and undermine the US position in the world.
For some reason the phrase "aid and comfort" comes to mind. Yes, treason is what comes to mind.
This, of course, leads to the following response:
Again, I draw a very thick line between Snowden's two sets of activities--revealing that the NSA was doing questionable things in the US and revealing America's secret activities in the world. Naive folks may think that gentlebeings do not read each other's mail, but in international relations, you don't have to be a Realist to understand that spying and counter-spying is endemic to the enterprise.
A caveat--I have not written much on this before because I am very ambivalent about much of this. I have long been frustrated with Obama's policies on surveillance, secrecy and all that. Still, I cannot help but consider Snowden a defector. Maybe it is that I grew up during the Cold War, but anytime an American flees to Moscow, I have to question their motives. And when they do so while carrying heaps of American secrets on flash drives, I develop some assessments.