Comment 17 for bug 857651

Another use case is corporate. Desktop roaming in an AD environment would result in your PC being populated in the greeter by anyone who happened to use your PC while you were on holiday. Or if support staff login to check a support call, or if we get the user to login at another PC to troubleshoot an issue.
So the use case is still aesthetics, but in my environment at least, you'd have greeters with 10+ entries on each PC and a lot of angry and confused staff wondering why they see all this spurious stuff on their login screen.

Finally, it's obviously detrimental to security that cleaners can glance at login screens to gather a list of valid usernames. There might be other ways to do this as a cleaner, but Ubuntu's greeter makes this stupidly easy.

As a wishlist item, therefore, I'd like the greeter to support the concept of "only ever show this user". Not sure what to log this against though?