UNC Charlotte has a trial subscription to the National Security Archive database, which I hope very much becomes permanent (which I've recommended but have no control over). It is both fun and interesting to read through documents, which are also useful for class. It also makes me wonder, not for the first time, what is being blacked out or not, and and why.
Take, for example, this short CIA 1976 intelligence assessment on the Somoza government's response to the Sandinistas.
What I thought was funny was the sloppiness on page 2. The CIA employee was getting bored. Further, though, the analysis is nothing a newspaper reporter wouldn't already know. Yet a big chunk of it is still blacked out.
The U.S. government has been obsessed with blacking out lots of stuff related to U.S.-Uruguayan relations in the 1970s as well, but the blacking out is just lazy. It's unclear whether the censors even know the material. The State Department Office of the Historian has complained about the ridiculous attitude of secrecy toward the 1954 Guatemala invasion. Meanwhile, the U.S. Congress actually voted not to release documents related to U.S.-Argentine relations in the 1970s.
The bottom line is that much of this secrecy is some combination of laziness and embarrassment. The U.S. government does not want to admit what everyone knows, namely its support for repressive governments and its complicity in serious human rights abuses. We'd be well served, however, by owning up to them and committing not to repeat them.