Mailing physical DVD's around... no, that's just ****** stupid, unless you're aiming for Hill Billy Ville where they are still using 56k modems.
Something along the lines of Spotify or Grooveshark on the other hand... yes, that would be popular.
The porn industry is hard pressed for profit as it is already though. P2P and [disliked sites that gives ****-links] and the similar make it way too easy to get hold of enough materials to get off with. I doubt that enough production companies would sign up for it.