> A phone number uniquely identifies an individual As someone who travels a lot I can attest to the annoyance of messaging apps which identify users by phone n

> A phone number uniquely identifies an individual As someone who travels a lot I can attest to the annoyance of messaging apps which identify users by phone number. WhatsApp is a good example. Another terrible design is one time passcodes which are sent over SMS. When a number gets recycled it can become impossible to recover access to a service which you forgot was associated with the number you had at the time of signing up in another country.