To Josh and wraith808:
So what you say is that, for example, W. Mark Felt was wrong to leak information about the illegalities committed by the Nixon administration?
In my opinion, the rule of law should be above any other rules in a state because it is the only thing that (at least theoretical) makes us equal no matter of our origins or of our wealth or of our connections. So, when someone breaks the law, he must be prosecuted and, if found guilty, punished. When a person working with classified information discovers that crimes or irregularities have been committed, it should be his moral (and hopefully legal) duty to inform the appropriate authorities. If they do not do their job (as it sometimes happens), it is usually in the public interest to know about those crimes and irregularities because the public opinion will change the way the authorities will do their investigations. This is my view on this subject and I will need some strong arguments to change my opinion.
As I said above, I do not consider what this person has done to be whistleblowing. I agree with you, wraith808, in the intel field you might have only bits of data and would be hard for someone to understand the whole picture. And if this happens, then you cannot tell what really happened so you have no reason to whistleblow (if it were the case).
I do not consider that it is a general rule that classified information only covers illegal information. That would be absurd. Quite the opposite, it is important to have data classified, in order to protect national interests. But when it is used to cover illegal activities, I do not agree with it anymore and I am glad that people break the silence in order to inform us of the government's illegalities.
Indeed, I do not work with classified data, so I do not know all the details regarding this subject. I only read some stories about some whistleblowers, people that have put their careers and even lifes in jeopardy in order to stop bad things and bad people (or at least to inform us about their existence). And I am glad that they did it.