In February, the retail behemoth agreed to buy the smart-TV maker Vizio for more than $2 billion, potentially giving Walmart a windfall of intimate consumer data. Smart TVs not only monitor what we watch with Orwellian precision but track other nearby devices with ultrasonic beacons, and can even listen in to what we say in the privacy of our own homes. Vizio specifically has been fined millions of dollars over allegations that it illegally spied on customers.