I'm not sure exactly how they do it here, but I can join my computer to the domain at any time, but only my computer. Thus, typing my domain account info is valid to join computer A to the domain, but not Computer B.

To request a new computer to be joined, we either fill out a web form or call IT (and they do the same process with the extra field of "username").

So there are ways to limit this. I'll try asking around and see if the IT guys on site know how it works.