To answer in a more explanatory way.
The multi GPU mining rigs act like they are separate computers as well. I got a 5970 and a 7950 in my mining rig. Thats a total of 3 GPU's.
You can make the cgminer config in a way that each GPU would mine a different coin (diff. pool) by stating an address and user/pass for each of them, or just leave one pool with user/pass and all the GPU's run that.

So the short answer, as it was answered before, is yes. Otherwise people would have to create lots of accounts in order to use more mining rigs