Chris Hedges published his introductory statement to a debate on that subject at Oxford University (which his side won, against a team of former US intelligence officials and pundits). It's brief and worth a read.
Snowden had access to the full roster of everyone working at the NSA. He could have made public the entire intelligence community and undercover assets worldwide. He could have exposed the locations of every clandestine station and their missions. He could have shut down the surveillance system, as he has said, “in an afternoon.” But this was never his intention. He wanted only to halt the wholesale surveillance, which until he documented it was being carried out without our consent or knowledge.
Worth remembering, if Snowden had really wanted to damage the US, he could easily have done an helluvalot more to damage us than he actually did. How do we know he didn't? Well, apart from Snowden and Greenwald's assurances, it's been almost 2 years since the date his documents were downloaded... the NSA has started to compile a list of what he took... do you think anybody would sit on that information for 2 years, and we wouldn't hear about the sudden checkmating of all our strategic operations, or else the ransom they wanted in exchange?
When I assert that Manning and Snowden have done no damage worth speaking of (compared to the value of their revelations), opponents tend to fall back on "Well they broke their oath to keep these things secure, that makes them traitors." Yet every elected official swears an oath to uphold the Constitution, including the 4th Amendment, howcome you're not calling them the oathbreakers? Manning and Snowden simply felt their oaths required them to reveal this stuff, while President Obama and security officials all the way down, felt their oaths permitted them to violate the plain intent of the 4th Amendment, and keep it all hushed up. Breaking an oath is not so clear-cut an issue as conservatives would like to believe.