Which then requires: 1. every site to obtain some automatable way to send text messages, which can get mildly expensive, 2. people to acquire at least one bur

Which then requires: 1. every site to obtain some automatable way to send text messages, which can get mildly expensive, 2. people to acquire at least one burner phone for authentication because they don't want $randomwebsite to have their real phone number, and 3. users to give up some degree of anonymity because the country of origin can't be hidden behind a proxy, as the phone number gives it away. This sounds like an overall loss for everybody to me.