I used to be in the intelligence field, and I held a top secret SCI clearance for about five years. What most people don't realize about classified information is that it's not the information itself that's so sensitive; it's the means via which such information is acquired that must be protected. If this were not so, targets could simply sidestep our intelligence collection vectors. I rarely dealt with any classifie…
I had a "Secret" clearance twice upon a time. Absolutely nothing I saw while I had that clearance was of the slightest interest. In fact, everything that I knew that was classified ended up appearing in Aviation Week. And no, I wasn't the leaker. But I regard that as a symptom of over-classification, and speaks directly to the "fifteen or twenty" clearances Kissinger was about to get that were above a Top Secret. Ult…
It's about compartmentalization - a guy who works intel in Iraq doesn't need to know about North Korean intel collection techniques, so it's classified differently and compartmentalized.