The number of people watching broadcast TV with the aid of an antenna is a fraction of what it used to be; about 90% of U.S. homes tune in these channels via some form of pay TV. If Fox decided to shut down its transmitters tomorrow, it would cut off only 10% of its viewers, many of whom might quickly sign up for cable just so they could keep watching "American Idol." And doing so would not only end the threat Aereo poses to the retransmission fees Fox receives from pay-TV operators, it could conceivably enable them to demand higher amounts from those operators -- and from the Aereos of the world.