Well, tube sites have ads going to dating sites. Dump the porn, click here to find someone and screw each other's brains out. Tube sites will always have someone buying ad space. The solution, if you ask me, is interactivity. Wanna know what it's like to do it with pornstar X? Buy the interactive DVD. That's impossible to rip on tube sites. Even a dvdrip torrent is useless because it destroys the interactivity.

Making sure everyone buys and does not pirate? Simple, offer some sort of hardware enhancing interactivity. Without it it's not fun anymore. There you go - torrents, tube sites, anything is down the toilet. Maybe there will be a new problem, people who clone the equipments and sell them cheaper, but that's already a different story.