It's the mystery that keeps us going. :) I for one was intrigued by River's words when she first emerged from the cryo-box: "They want me to talk..." The impression I got after my very first viewing was that she was referring to the rebels who "rescued" her, because they wanted inside information as to what was going on in the facility where she was being kept. But then I think about how much they risked to get her out, and for so little relative gain.