People often consider privacy to be a right, similar to having the right to move around, say whatever you want, and buy whatever you want. It's what some would call a "negative" right, meaning that it's something that people can't impede you from having. If I have the negative right of movement, that means that people can't keep me from moving from one city to another city. Contrast this with a "positive" right. A positive right is a right to something that imposes a cost to other people. For example, having the positive right to an education means that you are entitled to something that costs other people money, namely an education.
So, privacy is a negative right. It doesn't cost anyone any money to give you privacy.
What I wonder about is why people think that this is so important. There are familiar cases in which society faces a trade off between privacy and security. Having more privacy across the board may make it more difficult for law enforcement officials to acquire relevant information regarding criminal activity.
Also there are familiar issues associated with social networking. People raise a fuss about their privacy potentially being compromised on sites like Facebook. But why does it matter so much? Again, why do people place what seems to me a disproportionate amount of value on their privacy?
The explanation that makes most sense to me is grounded in the idea that information is a form of social currency. Having more information gives you a kind of power, and being exposed (i.e. having people gain information about you) somehow diminishes your power.
So maybe privacy is a form of empowerment. The less people know about you, the more "powerful" you are, perhaps. It's like a game of poker, where the person who has the most information about their opponent is most likely to win.
Suppose that all information was freely available. You could find anything you wanted about anybody, including classified government information. Likewise, anybody could find out anything they wanted about you. Nobody could hide any information at all. Would this be a better society? I'm inclined to think that it would be, but that's just a knee jerk response.
Basically, my gut response is that privacy is an issue only when it's asymmetric. What I mean is that I'd get upset about my privacy being violated if I didn't have equal information access to the individual getting my information. If had the same kind of access, i.e. if there was symmetry of information access between myself and some other individual, then I'd be okay with that. I figure other people wouldn't be, and I wonder why.