Maybe it's a bit of both.
Conversely, if a Prince has good news, and delivers it all at once but with no follow up, people will stop being grateful for what they've gotten, and will start demanding more, which can bankrupt any ruler who tries to comply. Likewise, if there's a steady drip of bad news, minds race ahead, anticipating worse to come and making advance preparations which undermine the stability of the Prince.
This basic psychology works the other way as well. If you have bad news about your adversary, and drop it all at once, they can take the hit and move on. But if you can supply a steady drip of negative stories it becomes impossible to get past the growing sense of distrust, especially when people start imagine the worst, and demand to see proof that their darkest fears are unfounded. This may mean having to prove a negative, which is the epitome of an impossible situation. Reaching this point only accelerates the downward spiral.
Of course, following this strategy means being able to place yourself beyond the reach of retaliatory efforts. It's what Sun Tzu would refer to as selecting the field of battle to play to your strengths while offsetting your weaknesses. If your chosen position also has the inverse effect on your opponent, neutralizing their strengths while amplifying their weaknesses, then it's a double win.
So far, Snowden's strategy has been textbook-perfect.