It’s not just emails and text messages that are at stake here. Devices such as the Apple Watch, and its successors, could soon be accumulating data about our blood pressure, sleeping habits, even our genetic make-up. On the face of it, this is as much of a threat to our privacy as government surveillance, if not more. Yet Apple and Facebook and Google know we will only trust them with our lives if we feel we can trust them full stop. What keeps them in line is commercial imperative.