"The NSA planned to investigate at least 4,000 possible insider threats in 2013, cases in which the agency suspected sensitive information may have been compromised by one of its own"
Assuming that each insider threat corresponds to one employee, and that the total number of employees in the intelligence community is 107,035, this would suggest that at least 1 out of every 27 employees has been considered a possible insider threat. And if you were to only consider the employee count of the NSA itself (which we don't know), it would be considerably higher.
The side effect of that level of paranoia is that office politics becomes an extreme sport. If you can make it look like the guy angling for the same promotion as you has a secret; or is actively selling out the country...
It may also explain some of the institutional rigidity we see in the IC's response to events. If questioning certain assumptions may get you not just fired, but jailed; and you value your career and your freedom, those assumptions become very hard to question. (e.g. the same assumptions that Mr. Snowden started questioning )
Assuming that each insider threat corresponds to one employee, and that the total number of employees in the intelligence community is 107,035, this would suggest that at least 1 out of every 27 employees has been considered a possible insider threat. And if you were to only consider the employee count of the NSA itself (which we don't know), it would be considerably higher.
This is... pretty staggering.