He has already martyred himself.
The question is why? Why did he feel he had to attach his personality to the leak? It's actually become an immense distraction from the core issue: PRISM
Well Manning did things your way, and he was discovered and locked away, tortured. Maybe Snowden knew there was no way to hide that it was him that leaked the data.
Rather than just disappear (thereby letting the NSA control the story and write his motives), he chose to make the first move.
In my opinion, he couldn't have done it better.
> Why did he feel he had to attach his personality to the leak?
Don't be obtuse. He chose to speak out, and still the NSA managed to tar him as an enemy spy. Had he simply disappeared, he would have made their work even easier.
Because it's not possible to keep who you are secret from the US government indefinitely. Better to go out into the open before they have the chance to smear you as a terrorist.
The media would write articles about who they thought you were - a chinese spy, etc.