I think porn companies would be very wary of accepting bitcoins for two reasons: The first being that the tech savvy people who use bitcoins probably all already know how to get good porn for free, and how to easily pirate all the good non-free stuff. The second reason is that the porn industry in the past decade or so has been a repeated target for the U.S. government over "obscene" content. I don't think many companies out there would be willing to go out and accept an untraceable currency with limited benefit under this much scrutiny.