If you assume the goal of all this is to deter future leaks, I'd say they are doing a pretty good job. Snowden has so much uncertainty and risk in the next few weeks that I bet borderline whistle-blowers are rethinking their plan.
Arresting him quietly without the media gets them Snowden, but not the deterrent.
If anything, seeing how those guys got treated is why Snowden fled the country. I can imagine that future whistleblowers are going to seek asylum first, then blow the whistle.
Whistle-blowers may be releasing information because of strong ethical objections, not rational thoughts about their own well-being.
I think watching this unfold with obvious lies from governments has actually strengthened the ethics in releasing this information, and may reinforce others with similar information that leaking really is the morally right thing to do.
Also the next guy maybe will leak anonimously, if that's possible with all that Prism systems.
Maybe creating some downtime in the system while the leak is produced??
If Snowden gets asylum in Russia after a few days of stress and uncertainty he is well ahead of Manning who's been held in conditions tantamount to torture. And he knew that was a possibile outcome before blowing the whistle and it didn't deter him.
On the other hand, if he gets out of their grasp, potential future whistleblowers will have a recipe for how to handle the situation and the knowledge that they can get away... It's a big gamble.
Arresting him quietly without the media gets them Snowden, but not the deterrent.