correct. I see my own, I see a few other people's, some windows usernames, and I used to think that was all of them until I read this article...

http://msdn.microsoft.com/en-us/library/ms187328.aspx

where it says "Any user can see their own user name, the system users, a sql user without login, and the fixed database roles. To see other users, requires ALTER ANY USER, or a permission on the user. To see user-defined roles, requires ALTER ANY ROLE, or membership in the role. ". But, if I don't know what I don't know, I don't have a username to ALTER...