Well if you post such a question on a publicy accessible forum do you expect only lawyers to answer? Of course not. You're also going to get different answers from a global persceptive based on different experiences and people will freely debate it. Which is whats happening here and theres nothing wrong with good fair debate. As for the advice that's gonna be given. If it's obviously wrong - like the tat guys - then other artists will want to warn the OP. Purely because they don't want the OP to get into any trouble. So yes you're right anyone doing this should get permission from the IP or copyright holder.

Pinky - you left the lens cap of your mind on again.