I assume the other problem is that public key infrastructure doesn't exist in a lot of places, whereas (almost) everyone has a webcam. I had the same thought a

I assume the other problem is that public key infrastructure doesn't exist in a lot of places, whereas (almost) everyone has a webcam. I had the same thought as many on this thread: all biometric identification is basically an arms race that moves along as new ways of gathering biometrics become convenient and ways of faking them are developed. But as you say, yubikeys also have problems. At some point it will probably be a hybrid, e.g. require a known acquaintance to digitally sign a video where you appear together.