Bamford was the first-ever NSA whistleblower, whose bravery led to the Church Commission and the unprecedented curbs on the agency's spying powers — his long, sympathetic Wired profile of Snowden is full of insight and wisdom.
There are so many passages in the article that I could quote, but the conclusion says it all:
But rather than the Russian secret police, it's his old employers, the CIA and the NSA, that Snowden most fears. "If somebody's really watching me, they've got a team of guys whose job is just to hack me," he says. "I don't think they've geolocated me, but they almost certainly monitor who I'm talking to online. Even if they don't know what you're saying, because it's encrypted, they can still get a lot from who you're talking to and when you're talking to them."
More than anything, Snowden fears a blunder that will destroy all the progress toward reforms for which he has sacrificed so much. "I'm not self-destructive. I don't want to self-immolate and erase myself from the pages of history. But if we don't take chances, we can't win," he says. And so he takes great pains to stay one step ahead of his presumed pursuers—he switches computers and email accounts constantly. Nevertheless, he knows he's liable to be compromised eventually: "I'm going to slip up and they're going to hack me. It's going to happen."
Edward Snowden: The Untold Story [James Bamford/Wired]