Get people talking about the gadgets they wish existed but don’t, and soon the idea of “glasses with a computer built in that tells you who you’re looking at” comes up. Such “augmented reality” devices seem so obviously desirable that someone usually says: “When will they start selling those, eh?” In fact, two different companies have built working prototypes in the past six years. Facebook had an internal version in 2017, fed by the colossal number of profile photos on its site. The other is Clearview AI, a secretive American startup that first came to the attention of the New...