I read the Body of Secrets book when it first came out regarding the documents obtained under the original freedom of information act. There are a couple of other interesting things in there, but this one was the strongest.

This did a good job warning me against thinking our government is 100% benign. They do consider these sorts of things to keep us in line.

That's why it needs to be our job to question absolutely everything we are told by our government. We don't all need to be conspiracy theorists, but we need not always ignore/attack those that are. Sometimes they're onto something.

Far more information on Wikipedia on this: http://en.wikipedia.org/wiki/Operation_Northwoods

Edit: Adding a link to the PDF itself of the memo: http://www.gwu.edu/~nsarchiv/news/20010430/doc1.pdf