I wondered about hotlinking too.
This is pure speculation like the majority of the posts- but I'd think if it's visible on
www.yourdomain.com then you need to have a 2257 statement somewhere.
If that was a way around the regulation then all people had to do would be to get a host outside the US and hotlink from their US based domains.
I doubt "It's not actually on my domain - you just see it on my domain" will be a good defense.
From a non technical standpoint it is reasonable for people to think you are responsible for what is shown on your domain.
Probably none of those question like you came up with would be anwered until a case went to court.
