I certainly agree that there's a difference between public and private information. Whenever you post something on Facebook, you are able to choose right then and there whether that information will be publicly visible, whether it will be visible to your friends, or whether it will be visible to a narrower category of people.
One of the things we've invested in very heavily and which I think we need to invest more in, as Kevin mentioned, is transparency around advertising and, specifically to your point, the specific information or the specific interests that are used to judge what advertisements to show to people.
That means a couple of things. It means there are some things we shouldn't make available for targeted advertising at all. Second, it means that we should tell people—and we do tell people when they see particular ads—why they're seeing those specific ads. In my earlier example, if we think you're interested in cars, we'll tell you that that's the reason. Third, we need to put people in control. If they'd prefer not to see ads based on particular kinds of information, they should be able to do that as well.