We are responsible for the technology that shapes our lives. Depending on how we design it, people may become unaware of the technical manipulation they are privy to, or have more control in creating innovative, personal experiences. We need to let the user be the agent of their own experience (and shape the experience to their needs and wants, not the other way around)
The reason to fear Facebook and its ilk is not that they violate our privacy. It is that they define the parameters of the grey and mostly invisible technological infrastructure that shapes our identity. They do not yet have the power to make us happy or sad but they will readily make us happier or sadder if it helps their earnings.