JerkStore: So it's like just anybody can walk off with top secret stuff and it's no big deal? Is there no accounting system to keep track of where the documents are? Hell, even the elementary school library has a very effective way to know who has one of their books.

That's an interesting question.  Elementary has a pretty elementary problem space in comparison so we can't really compare to that.  Would have to be something much bigger and distributed like the complete public library system--possibly spanning networks because there's private contractors and all that.

My guess is that they actually lose a lot of books and just have no idea where they went.  With modern computer systems they're clearly a whole lot better at it just like the FBI is much better at distributing information.  Go back many decades though and you're talking about individual, local computer systems that MIGHT be able to dial into something and communicate on an open wire (telnet instead of ssh for example).  Previous to that you have written logs and cards, which for an elementary school is fairly sufficient.  So tracking then was already pretty prone to human error and this isn't more than like 40 years ago for advanced, well funded users of technology and skill.

Further, previous to the ability to scan and email documents easily the usual way to make sure documents were not lost when needed, say by an investigative team in the field, would be to xerox (and previous to this ... not done or done by hand) and let people go with them with the understanding they'd be destroyed later.  So easy for any individual to keep.  You have the same problem now and additionally you have all sorts of computers that might have logged the transmission of the document--hopefully encrypted but email isn't by default.  See the Clinton email server nonsense.  Even if it's encrypted though, today's secure is tomorrow's open line.

It would seem that information really, REALLY wants to be free.  It's a super hard problem to ensure it's contained.  That's why any human involved that willingly becomes a point of failure in the process of securing that information is a willing threat to its containment.  It's an all too human problem and I hope those who put it upon themselves to be responsible for stuff like Top Secret documents take the responsibility more seriously in the future.  It'll be easier for them to with advancements in security like Zero Trust and the ability maybe of image recognition to see if someone is trying to photograph the screen--something that's relatively this last second in terms of the history of national security.