[I love that title]
I was reading Mike's bizarre ramble on the difference between porn and art and felt like I might be able to contribute, mostly by filling in where Mike claims to lack exposure. The question as posed, before Mike meandered, was "what inherently separates pornography from sexually explicit art, and how [do] they create a dialogue with each other, and with culture in general?"
I have a number of disjoint thoughts at the moment, but I think they can be forced to align. First, the line between porn and art is subjective and depends on the current social norm. Lady Chatterly's Lover would no longer be considered pornographic by modern standards, even if at the time it outraged society. Similarly, I imagine a Sports Illustrated Swimsuit Edition would have been taboo at any time before the 1950s... just witness the progression of swimwear over the last twenty years! Cindy Crawford used to wear a one-piece, now the models have their "swimsuits" painted on! To flesh out the examples, think about what the troops get: now, they get all the porn they want, historically cheesecake paintings had to hold them over.
This is the problem with obscenity legislation, and why the community standards idea was the best way out. No other crime (that I can think of) changes with time. Murder was murder in 1500 and 2004, as were rape, theft, and assault. Obscenity.. well, a miniskirt would still be obscene in parts of the world today (cough, Islamic regimes).
So what is the line between them? I'd go back to community standards, to some extent. Porn is what I don't want people to know I have on my computer. Edward Weston photographs of complete nudity can be fine desktop patterns though! A certain element of shame separates the two.
To take a page from Mike's book, we can abstract this out. What about pornographic violence? Where does that term/concept fit? I felt sick and ashamed watching Kill Bill, and ended up walking out on it because I considered it a gross spectacle. Pornographic in this context seems to mean irreverent, excessive, vicious, and well, prurient. It's there to satisfy a base, reptilian urge.
Pornography is meant to be consumed, in private, furiously clicking, with one goal in mind and quickly forgotten. No one remembers porn (hell, I can hardly remember what it was that was arousing to me five minutes after the browser window closes). Sensual or explicit art can also titillate, but it's meant to work at more than a sheer animal, instinctual level. It's engaging higher reasoning, making you think about what is arousing, how everything relates, what the hell is the point of all this sex anyway? It's memorable, respectful, and probing.
I'm getting a little tired, so the rhetoric is starting to unravel a bit (attention span waning a bit). But I think the line between porn and art is easily summarized by how memorable it is, what it makes you think about, and what your community standards are.
As for informing... art is fueled by porn. As GIlmartin would say in Gothic Lit, "HIgh literature is reenergized and rejuvenated by themes from low literature." Porn is lowest of them all, and constantly pressing the horizons of art and fashion forward... (upward?)
... Ok, and now back to the Bible and Law (tomorrow maybe)