First was he lured to Russia by Assange (working for the Russian propagandastation Russia Today) and what is the prorussian function of Wikileaks today (different from the goals set at the outset)
Snowden and his closest supporters contend that Snowden flew from Hong Kong to Moscow on his way to Latin America when the U.S. government stranded him in Russia by revoking his passport. There are several reasons to question that claim, including the fact that WikiLeaks founder Julian Assange — who paid for Snowden's lodging and travel in Hong Kong — advised Snowden against going to Latin America because "he would be physically safest in Russia." http://www.businessinsider.com/why-edward-snowden-is-stuck-2014-4
But the biggest fear of the US intelligence community is that Snowden is living in a Soviet controlled environment
""He does not have the training to deal with this kind of situation," Russian security services expert Andrei Soldatov previously told BI. "Every time, he found himself in some new difficult circumstances and he was forced to make some decision. And long term, it's a very successful thing [for Russia]." So as long as Snowden doesn't reach a plea deal with Washington, the former CIA technician is stuck in a Kremlin-controlled environment." http://www.businessinsider.com/why-edward-snowden-is-stuck-2014-4
Every operative gets a special training for when he gets caught or how to handle specific psychological situations. And even if he doesn't have any access to the information - if that is true.
"And the classified intel in his head is what makes him so appealing to a U.S. adversary like Russia, especially because Snowden is not a true spy. http://www.businessinsider.com/why-edward-snowden-is-stuck-2014-4
there is still enough information that over time can be received from him, even if that is only the way people work, interact, pass tests inside the NSA which is very useful for infiltration and 'human intelligence' to combine with cyberoperations.
so in the end
“If there isn’t a deal, it’s an unfortunate but relatively stable thing for him to be in Russia for the rest of his life with an American indictment standing against him,” Daniel Richman, a former federal prosecutor and a Columbia University law professor, told The Times. http://www.businessinsider.com/why-edward-snowden-is-stuck-2014-4
and all the information he had laid his hands on has to be seen as compromised