There is a very robust debate going on between people who defend the behavior of Edward Snowden and (especially) Glenn Greenwald, and those (most recently, Michael Kinsley) who see Greenwald, Snowden et al as dangerously naive.
Martin Longman weighs in on the debate at Political Animal:
Too often, it seems to me, Greenwald and his strong supporters behave as if the government deserves to be damaged and that our national security ought to suffer, even though all Americans are put at risk as a result. The risk to Americans is not something that can just be shrugged off as if it were indisputable that the country has gained a net-benefit from every single disclosure of classified information.
The reason that Greenwald is getting the better of the argument isn’t because his principles are clearly superior, but because the government lacks credibility. The overall effect of the disclosures has been beneficial, at least so far, because nothing catastrophic has resulted and we now have greater knowledge about what our government has been doing, which is already leading to reforms.
But none of this relieves journalistic enterprises of the responsibility to weigh the risks and benefits of disclosing classified information, nor does it completely vindicate either Chelsea Manning or Edward Snowden, who both leaked far more information than was necessary to make their points.
There are no heroes here. Not among the government snoops who vastly exceeded what should be permissible in a free and democratic society, and not among the scolds who took it upon themselves to release massive amounts of classified information.
We need credible and effective systemic oversight mechanisms. Otherwise, we are left to depend upon the judgement of self-righteous whistleblowers and their enablers who see the world only as black and white, and who have never considered whether even virtuous ends justify their chosen means.