I think bitcoin and porn would be an excellent mix overall considering how people would prefer to maintain there privacy when it's related to things like that, Here you don't have a payment to a porn website in your CC statement but this one is just a number to a privately generated address.
Indeed basically bitcoin is a digital currency that gives privacy a very secret to everyone. so indeed bitcoin is used by a variety of things that do require privacy very closed. Same thing with porn or dark market, all of that is the Foundation for the growth of the bitcoin or things that make bitcoin can grow the better (in my opinion)