I'm tired of hearing this: If I have nothing to hide I have nothing to fear. There are so many things wrong with this phrase, yet so many people repeat this whenever there is a discussion about the latest story about governments spying on everyone.
Sometimes you might have something to hide and fear. Sometimes having something to hide is the right thing to do, even though the society you live in clearly defines your actions as being highly illegal.
When you invite the "authorities" in to your private space, only because you have nothing to hide (and terrorism) then you are opening other people's doors too.