Real pirate hunters...
 

Ok so not in the "Harr harr" peg-legs and parrots type of pirates, but the internet pirates that rip pretty much every major porn DVD onto torrent sites.

Surely some of the big guns (DP, Vivid, etc.) would have the funds available to stop it, or at least trace people in much the same way as hollywood does. So how come I've never heard of anyone being busted for ripping off a porno from the net?

Because there's no umbrella organization to represent porn producers in cases like these (something like the RIAA or MPAA) and porn producers bark way more than they bite, while refusing to play with others.