Would this really be of much use anyway?
I have always believed "If people want to do / access something badly enough (such as XXX content) they will find a way, no matter what obsticles are in there way!".
Plus as well, I don't think the adult
website hostings will like this one bit as popular names would be wanted by more than one company whereas at the moment each popular name can be registered under loads of TLDs such as .com .co.uk .us etc for loads of different companies