When I first went into the Air Force (1972) I needed a Secret clearance for my first assignment. Filled out all the proper forms, gave the references, etc. The Secret/NAC (National Agency Check) was a breeze for an 18-year old right out of high school, who had ever only had two addresses, and only a few trips to Canada on a Civil Air Patrol cadet exchange program.
Around 6 years later when I required a Top Secret/SBI (Special Background Investigation) for a new assignment the paperwork was a lot more involved. I had to remember building numbers and dorm room numbers that I had occupied for the previous 6 years. Needed more references...and at that level, they really didn't seem to care so much about *those* references, but they asked each of them for additional names of people that knew me...*those* were the ones that they really talked to the most, and not the ones that I had given them.
After getting the clearance, I then had to go through additional checks and training for higher and higher levels of access. Even though I worked in a completely secure building (we went through a guard station on the way into, and out of, work), if I walked down the wrong hallway and didn't have the correct tab attached to my chain alarms went off and I had to wait until someone came to escort me away from the area. Some of the computer rooms in the extremely secure building had a mantrap with a guard that checked each person trying to gain access.
All very serious stuff. I can't imagine that with the level of ineptitude exhibited by these clowns they are still being allowed to have access to our most closely held information. If I had intentionally omitted any relevant information from the forms and interviews I would probably still be sitting in another type of secure facility, where they fed me every day and gave me access to an exercise yard for an hour a day, and where I might be able to actually see some daylight through the bars.