There really does have to be a tight set of expectations in this regard. People can't just spill the beans every time that the think it is morally justified. Look at how disparate the views of what is right and appropriate vary n this board alone.
It's pretty clear that one thing that the US will be doing in the future is limiting the number of civil contractors who have access to sensitive information.
One of the big reasons that I am not willing to side completely with Snowden is that he took an oath - and he broke it. He knew there would be sensitive info when he took the oath.