Well, most people have email and the ISP can just require that they have a working email address on file. That's how ISPs in Germany do it and it works fine. O

Well, most people have email and the ISP can just require that they have a working email address on file. That's how ISPs in Germany do it and it works fine. Or if it's urgent, they'll just call you. No need to invent a new form of communication or do evil things with Squid.