"I've got nothing to hide" isn't the only argument that is used to counter privacy advocates, and I agree that this argument is wrong to some extent. A more valid argument might be that when I think of government agencies looking at data from Google I know I'm just a number, unless they want to investigate, in which case they may look at my personal info. But I have to guess the number of investigated people is pretty low and there must be valid reasons to start an investigation, just like they need a warrant to get inside a house. It would simply be impossible to investigate every one of us in detail.