Implying that one would remember their email address but would forget the 2nd item for identity. Combining email address with another string to create a unique

Implying that one would remember their email address but would forget the 2nd item for identity. Combining email address with another string to create a unique ID isn't the answer either. Any combination of string+salt can be broken. What we are getting at is that it shouldn't be on the user to have to remember yet another identifier for XYZ website or service. We already have the concept of usernames, email address are somewhat unique, and you can suffix numbers like they do. If you really want unique ID's, decouple login from your identifier. On Steam, people login with their username or email address, not their Steam ID. For some, their Steam ID is 9999999999999999 long. For others it's 99999999 long. It all depends on when you joined Steam.