I believe most of the most profitable porn enterprises, like, for example, Vivid Video, are private. I believe many stay private for various reasons. First of all, some are afraid of public scrutiny that might come with a stock offering. Up until recently many porn producers in California did not even have signboards outside their studios announcing who they were. Also, they probably like to stay private to keep the business under their (the owners') control. Although these enterprises may not be quite as lucrative as people believe, they still appear to generate enough cash to make a stock offering superflouous in some respects (they don't have a business need to raise funds). However, I guess sometimes the owners may be too impatient to skim proceeds off the enterprise over a 20-year period (through salaries and other stuff to the owner) and may hope that a stock offering may quickly make them rich.
I am not going to discuss the economics of the business in general, such as the phenomenon that anyone who has a digital camera can now become a porn producer if they want to. Also, like the defense industry, it's sometimes hard to say where the industry begins and it ends. Is a video store owner that carries porn part of the industry? Maybe, if the few titles this person carries generate the majority of his or her profits...
Despite the fact that the vast majority of porn is still a private industry, I believe the porn stocks are a good way to track the industry's overall health from the outside. You might, for example, add up all the revenues from all the companies and then track the totals on an annual basis to estimate growth; I have not done this.
Playboy (PLA). Playboy is Playboy, but what some old timers may not know is that they do produce straight-out hardcore porn in addition to their tamer magazine.
Lodgenet (LNET) They do pay-per-view movies in hotels. Who knows what their exact profit breakdown is between porn and nonporn. Slogan "What you want...when you want it."
New Frontier Media (NOOF) I believe this mainly does streaming porn over the internet.
Private Media Group (PRVT) This is a European porn producer that both shoots its own porn films and distributes them over various outlets, mainly in Europe.
Metro Global Media (MGBL) This is one of a horde of American porn studios, except this one happens to be public. From what I've gathered in the past it produces fairly low-grade stuff, neither noted for its production quality nor originality.
Rick's Cabaret (RICK) This is a strip club. So, I guess maybe to some it's not porn exactly. Go to their website and you can see the flesh of some of the "Rick's Girls".
Also, I should mention Beate Uhse, the German sex shop, but that is listed in Europe, not in America.
There may be other "porn stocks" I have missed, particularly in Europe.
I suppose if Bill Gates or Warren Buffet were anti-porn crusaders, they could buy up all these companies and shut them down. However, the entrepreneurs would just take the proceeds from their companies and run across the street to open the same business again, with all of the screen and behind-the-scenes talent following them.
I guess my only hope to turn the tide with porn would be for each person individually to stop watching it, kind of like the "throw out your TV" phenomenon. I expect that to happen as much as I expect people to voluntarily to switch to wearing the scratchy black clothing the Puritans used to wear...