That's a truism, but oddly at least one Supreme Court Justice thinks that the US Constitution hasn't changed. See http://www.claremontmckenna.edu/salvatori/publications/RARSc... for some elaboration.

I personally think this is a perverse view, leading to weird contradictions like the "Third Party Doctrine".

Given the history of US intelligence agencies (COINTELPRO, SHAMROCK, etc), my main thought is that they're a bigger threat to me, my family and my country than just about anything else.