Indeed, extortion is the major value in any surveillance system. It is a central admitted activity of spooks, used to "turn" "assets", and then to keep them producing. It is a central activity of the FBI, and prosecutors, with admitted use to "turn" witnesses, and even drive them into life-threatening situations while "wired" with audio, and lately video recorders or transmitters.
Of course the uses admitted in public are far from the only uses.
You can be harmed with information not even about you. It could be about a relative, or a relative of a prosecutor, or a judge, or landlord. Try to imagine the power available to Google, Facebook, Amazon, AT&T, and Sprint over the employees of the legal system and over politicians, and their staffs, on the basis of their detailed data collections, including live audio and images.