A couple of sites I use have a username, second identifier, and a password.
One site (ADP payroll) has client id (company's number) user id (my ID) and password. My company's id is 5 or so digits that mean nothing to me. Since it is a number, I just type digits, and delete them until the form-filler remembers what I typed last, but it's not optimal.
The second site (Australian Phone Company) uses username, password and "account name". At least this time it is a string I can remember, but it's still annoying to have an extra field to fill in.
These additional fields aren't additional security, they are just user name space dividers.
Is there a way to get them auto-filled like the username/password fields are?