Frankly, I don't think any of these questions matter, and the speculation without evidence is not useful. We should be discussing the leaks, not Snowden's motivation in leaking, his background, his girlfriend, how much he understands of what he leaked etc. The motivation of a source in journalism is not really important, what is important is discovering the truth about what is happening in the world and our true relations with our government.
What's more, Snowden apparently thought the entire set of slides should be revealed to the world. I'd like to know what changed his mind.
Snowden gave the documents to journalists so that they could fact-check, start asking questions, and release what they thought was appropriate. According to Greenwald he specifically mentioned that he didn't want to dump all this data, and I can see good reasons why he wouldn't want to - there are probably things in the documents that would be very damaging (and not just to reputations) if released, some documents have been redacted before release, and they require explanation and context - none of that comes with a simple dump of the documents.
There are also sound tactical reasons for allowing the administration to tangle itself in its own lies, and to prevent the story simply being buried so I completely understand why they do this. Of course the newspapers and journalists involved have their own opinions, but trying to reduce those opinions to left wing or libertarian or whatever other labels you care to apply does nothing to elucidate how they have affected the presentation of the information. On the contrary, it just allows people to dismiss the information without bothering to address its implications. Greenwald for example has been labelled extreme left-wing, libertarian, extreme right-wing and everything in between, but I think he's really interested in privacy and surveillance, not joining the left-wing or right-wing club and hating the other side. The Guardian has not pursued an agenda here that I can discern aside from trying to sell more newspapers or get more hits - they've printed stories from all over the political spectrum, and they are not the only newspaper releasing stories - the most important recent leak of 4 slides was from the Washington Post, which is also in possession of this material, papers in Hong Kong and Germany have also been given some information. Snowden was also interviewed in Hong Kong by veteran diplomatic reporter Ewan MacAskill[1] who seemed impressed with his credentials and honesty so he's not completely opaque. I'd recommend any who haven't to watch this interview with the Guardian editors explaining the process in a bit more detail[2].
I find the disturbing allegations of unregulated, widespread, and deep surveillance used for economic and political ends far more important than Snowden's role in all of this, and I think he'd agree with that. While it's tempting to get obsessed with Snowden, his character, his job, why he leaked etc, and create grand conspiracy theories surrounding it, it's more healthy to discuss the facts we do know and their implications for how we use the internet. More information will come to light in time, and the information we do know raises serious questions about just how far state surveillance should be allowed to go.
[1] http://www.guardian.co.uk/profile/ewenmacaskill [2] https://www.youtube.com/watch?feature=player_embedded&v=7pdz...