The NSA’s voice-recognition system raises hard questions for Echo and Google Home

Suppose you’re looking for a single person, somewhere in the world. (We’ll call him Waldo.) You know who he is, nearly everything about him, but you don’t know where he’s hiding. How do you find him?
The scale is just too great for anything but a computerized scan. The first chance is facial recognition — scan his face against cameras at airports or photos on social media — although you’ll be counting on Waldo walking past a friendly camera and giving i