Maybe ask them how they would feel if a little robot owned by some giant corporation was following them around every day, all day long. And imagine the corporation had similar robots following everyone else around, even children. And tell them the corporation made its money by selling the information it collected to anyone who could pay. And tell them some of the purchasers use the information for various nasty things, like identity theft, And then ask them how they would feel if the robots were invisible, so they didn't realize they were being monitored. And then tell them that is what is actually happening today.