I don't know about that. It's an interesting question. Maybe the iTunes as the source isn't the best example (although it could be exactly the same, I dunno). What if you have a film on your ipad and want to push it to an ATV. If you have more than one, I wonder if you need to designate which it goes to. I'm guessing you do, and that it wouldn't go to all three (if you wanted it to).
Another question is can an ATV in one room pull from iTunes while another in another is pulling a completely different movie at the same time?