The most striking thing Snowden has revealed is the depth of what the NSA and the Five Eyes countries [Australia, Canada, New Zealand, Great Britain, and the US] are doing, their hunger for all data, for total bulk dragnet surveillance where they try to collect all communications and do it all sorts of different ways. Their ethos is "collect it all."

In all my work, I'm interested in understanding big issues through the lives of individuals.

So my first experience was that I had to do a reboot of my expectations. Like fantastic, great, he's young and charismatic and I was like wow, this is so disorienting, I have to reboot. In retrospect, I can see that it's really powerful that somebody [Snowden] so smart, so young, and with so much to lose risked so much.

One of the most frightening things, I think, is the capacity for retroactive searching, so you can go back in time and trace who someone is in contact with and where they've been.

I was in correspondence with an anonymous source for about five months and in the process of developing a dialogue you build ideas, of course, about who that person might be. My idea was that he was in his late forties, early fifties. I figured he must be Internet generation because he was super tech-savvy, but I thought that, given the level of access and information he was able to discuss, he had to be older.

In terms of sources coming forward, I really reject this idea of talking about one, two, three sources. There are many sources that have informed the reporting we've done and I think that Americans owe them a debt of gratitude for taking the risk they do.

Snowden has presented us with choices on how we want to move forward into the future. We're at a crossroads and we still don't quite know which path we're going to take. Without Snowden, just about everyone would still be in the dark about the amount of information the government is collecting. I think that Snowden has changed consciousness about the dangers of surveillance.