I like this explanation of the importance of privacy from Glenn Greenwald, who has been the main outlet for all things Snowden:
And let me just say one other thing: sometimes it is hard to convey why privacy is so important, because it’s kind of ethereal. But I think people instinctively understand the reason it’s so important, because they do things like put passwords on their email accounts and locks on their bedroom and bathroom doors, which reflect a desire to keep others out of certain spaces where they can go to be alone. That’s a way of making clear that they value privacy. And the reason privacy is so critical is because it’s only when we know we’re not being watched that we can engage in creativity, or dissent, or pushing the boundaries of what’s deemed acceptable. A society in which people feel like they’re always being watched is one that breeds conformity, because people will avoid doing anything that can prompt judgment or condemnation. This is a crucial part of why a surveillance state is so damaging — it’s why all tyrannies know that watching people is the key to keeping them in line. Because only when you’re not being watched can you really be a free individual.