Many Web 2.0 applications collect their users' data -- bookmarks, photos, music tastes, and much more -- and make that data more useful by aggregating it, sharing it, and remixing it. What does this approach mean for the users who are creating that data? What obligations do these businesses have to protect the people who are contributing of themselves to build these applications? We'll look at different approaches a Web 2.0 company can take, and how they have worked for businesses in the past; and we'll explore what promises a business can make to help their users feel and be more comfortable sharing their data online.