And there is the blackmail angle-----If You Don't Care About The NSA Because You 'Haven't Done Anything Wrong,' You're Wrong

If You Don't Care About The NSA Because You 'Haven't Done Anything Wrong,' You're Wrong | Techdirt:
Cardinal Richelieu's famous line is:

If you give me six lines written by the hand of the most honest of men, I will find something in them which will hang him.

It's easy to twist almost anything to be used against you if someone cares enough. 
And with a legal code that means people are committing, on average, three felonies a day (at least according to one estimate), it can be even worse. 

That's worth keeping in mind any time someone writes off the NSA as not being an issue for them because they've "done nothing wrong." 
Driving home that point is an excellent short "Op-Doc" in the NY Times by filmmaker Brian Knappenberger, which has brief interviews with a bunch of great people (many of whom you'll hopefully recognize) explaining in very clear terms why you should absolutely care about the NSA. 
There are many reasons discussed, but a simple one, highlighted by David Sirota, goes back to that quote above. 
You can claim that you've done nothing wrong all you want. 
However, if someone really powerful decides they want to railroad you, you'd be surprised at how much it can be made to look like you've "done wrong." 
And when the NSA (or the FBI) can readily access all sorts of data about your life, their ability to build such a story increases tremendously.