Last.fm automatically generates a profile page for every user which includes basic information such as their user name, avatar, date of registration and total number of tracks played.
Unlike purely anonymous remailers, it assigns its users a user name, and it keeps a database of instructions on how to return messages to the real user.
While some systems may simply distinguish between privileged and non-privileged, systems commonly have a form of requester "identity", such as a user name.