PORN: BUSINESS OF PLEASURE. 9 tonight, CNBC.

SEX SELLS, even when it doesn't.

And that's probably all you really need to know to understand why CNBC tonight has Melissa Lee looking into the $13 billion porn industry.

Backed by a plethora of suggestive clips and the even more titillating warnings of "mature sexual content," "Porn: Business of Pleasure" is one of those documentaries that news organizations do periodically to help keep the lights on.

Because it's a cold, dark world out there, what with that series of tubes known as the Internet and all the other distractions that draw away people who used to watch television and buy CDs and even (gasp) read newspapers.

And it's apparently even getting a little chilly for the pornography business, which, according to Lee, "is fighting for profits" as technology screws with its business model.

Here I must confess that this actually was news to me: The one industry I'd assumed had figured out how to profit in the Internet age was porn.

Followed closely, of course, by a select group of Nigerian princes and their bankers.

Turns out, though, that some of the same people who believe information wants to be free feel the same way about scenes involving three-ways.

In fact, according to Wired magazine's Nick Thompson, porn's now facing the same challenges the music industry is.

"They've responded slightly differently, but we've seen the music industry transformed" through file-sharing and an increasing belief that albums should be "only be available for free," he tells CNBC.

Of the top 100 most-visited Web sites, five are porn tube sites, reports Lee, noting that all five of the video-sharing sites get more traffic than WashingtonPost.com, Match.com or Bank of America's online banking site.

No surprise there, but that's a headache for the men and women whose companies' paid-for porn is showing up online.

As one exec notes, the porn tube sites will take down copyrighted material if there's a complaint, but that "now we have to spend money policing the Internet. I don't think that should be our job, but unfortunately, no one else is doing it for us."

Sir, there are people at a number of networks that deal with YouTube who might feel your pain.

Interestingly, though, the porn exec thinks the answer may ultimately lie in a model that sounds a lot like, well, network television, suggesting his company might someday be giving the movies away while becoming advertiser-supported.

"Pornography has been around since the days of the caveman. It's not going anywhere," he concludes.

That fear set aside, Lee moves on to introducing us to Paul Little, who, she says, "may be the dirtiest man in America."

Little, whose screen name is "Max Hardcore," was just weeks away from beginning a 46-month sentence for selling and shipping obscene materials when he spoke to CNBC.

Jurors aside, "society has spoken," he insisted. "There's more people buying my videos than there are people protesting my videos."

And although there's plenty of footage of people hailing the 52-year-old Little - whose films feature him with women portraying underage girls - as some sort of hero, possibly the most telling indication that he's not all wrong is a shot that accompanies a different interview.

In it, Michael Leahy, a self-described porn addict and author of "Porn Nation" who tours campuses to warn students against pornography, is shown speaking to what appears to be a largely empty room.

Through it all, "Porn" veers dizzily between Serious News Documentary and soft-core movie trailer.

It probably doesn't help that the CNBC announcer at times sounds as if he's salivating as he tells viewers what's coming up after the commercials, or that a segment on women executives is introduced with clips of "what most people think of when they think of women in porn."

Which is apparently not the motherly looking blonde who explains that she's there to make sure her company's movies appeal to women, too.

"Women want to see the woman have an orgasm, too, not just the guy," she says. "I mean, how many movies do you see where the woman doesn't have an orgasm, it's just blah-blah-blah-blah till the end and it's him."

Jesse Jane, a porn star who wants to be the next Jenna Jameson, lets the cameras follow her home to Oklahoma City as we learn that Oklahoma is in the Top 10 of porn-watching states and that Jane in real life is Cindy Taylor, a wife and mother.

There probably are some guys who really don't want to be visualizing that.

But chances are they won't be getting their Jesse Jane fix from CNBC, anyway. *

Send e-mail to graye@phillynews.com.