From the speech given at MIT yesterday by former U.S. Ambassador to Saudi Arabia Chas Freeman:

Mr. Snowden has brought home to us that, while we Americans do not yet live in a police state or tyranny, we are well along in building the infrastructure on which either could be instantly erected if our leaders decided to do so.  No longer protected by the law, our freedoms now depend on the self-restraint of men and women in authority, many of them in uniform.  History protests that if one builds a turnkey totalitarian state, those who hold the keys will eventually turn them.

The punch line paragraph from a brilliant speech.