> If that assumption were to be violated then everyone would have to rethink their authentication systems, for instance, because there'd be no way to send passw

> If that assumption were to be violated then everyone would have to rethink their authentication systems, for instance, because there'd be no way to send password reset emails to people. I don't think that's necessarily true. Running email is simple enough that ISPs (to include mobile ISPs) could return to doing it for their customers. Heck, if you're a node on the Internet then by default you can receive email anyway …