... because this has happened how many times?
Folks have lost clearances and jobs. I don't know about prison time. But I do know the fear of these things happening is a motivating factor not to cross the line. But I'm just some guy...
The problem here is that you trust the organization to police itself, whereas it has little incentive to actually do so effectively.
The cases of caught individuals seem to have gone under-punished, as they sound worthy of prison time.
Also, even if the NSA polices against personal abuses, why would it police against systematic abuse for government's purposes against the constitution?
Self-policing does not work well, especially without elaborate mechanisms to enable it to work, and especially with a combination of secrecy and lack of oversight.
I'm not saying I trust it to police itself. I'm trying to suggest that the environment in which NSA analysts work does have a (positive) material effect on their behavior. Non-systemic transgressions are not common. When Snowden said he was able to check Obama's email, that angle was lost.
Now, systemic problems are a different issue. But the article we're all talking about here is written by an analyst from his own perspective.
You mean, besides his family, friends, and loved ones when he loses his job and potentially ends up in prison. You're underestimating the amount of training and internal oversight that occurs.