Mark Zuckerberg, founder of Facebook, recently shared a picture of himself celebrating a milestone: Instagram now has five hundred million active users each month. There was Zuckerberg in his office holding an Instagram-like frame in front of himself. The picture would have been unremarkable and quickly forgotten but for this: Astute observers noticed that his laptop was on the desk behind him and that he had placed tape over the camera and the microphone. Those are small but significant details. …