One of our attorneys is out of the country and visited a client's site. In order to get on their network, they mistakenly told him to exit our domain. Big time oops.
Of course, now the user can't log in to the system properly or access his offline email.
I don't blame the user in these circumstances because they are usually just listening to an incompetent admin at the site they are visiting. But you really have to wonder, why does Windows let a user remove a system from the domain when it doesn't let them add it? It shouldn't matter if the user has administrative rights on the PC, it should be an action that is only allowed if you can authorize yourself as a domain administrator at the time you want to perform the removal.
I'm sure that Microsoft has some well rationalized reason for not doing this, but I'm not buying it. I've seen this happen too often at the worst possible times and it is a behavior that should not be allowed by the OS.