Children used to learn about sex on the street – either from friends, those weird older kids who'd smoke behind the dumpster, or a friend's older and ostensibly wiser sibling. Web 2.0, of course, has changed all this. Instead of getting the goods from an unreliable source in person, a recent study suggests that kids are turning to the likes of YouTube, Google (GOOG) and Facebook, among others.

The study, conducted by technology security company Symantec (SYMC), puts expressions such as "sex" and "porn" at the top of search lists.

When it comes to telling lurid sex stories, CNBC is no virgin. Tonight, the business channel airs Porn: Business of Pleasure, following on the stiletto heels of The Business of High-End Prostitution from last year. CNBC this year aired a documentary on Nevada's notorious Mustang Ranch and last year ran an expose of hedge-fund manager Seth Tobias, who apparently lead a secret gay life with a guy named "Tiger" and drowned under mysterious circumstances.

But tonight's offering from the General Electric Co. (GE) channel focuses on the very real problems that adult-entertainment companies face. Like mainstream content providers, porn producers face numerous competitors who provide adult entertainment for free. Hustler's Larry Flynt and Girls Gone Wild impresario Joe Francis even argued -- jokingly, I think -- that the U.S. should bail out the adult industry to the tune of $5 billion. (Now there's a fantasy for you.)

For more than three years now, the adult entertainment business has been looking for something to help it survive. The industry is in crisis, with major brands collapsing, and legendary companies making desperate attempts to compensate for crashing revenues. While some are looking to mobile internet solutions as the hope for the future, other companies are tinkering with the basic formula of the business.

Since the late 1980s, the number of porn titles has increased substantially from one year to the next. Even after 2005, when the adult DVD market began its free fall, the numbers kept getting bigger; last year, production peaked at more than 15,000 new movies.

The dirty little secret behind many new technologies is porn. From cinematography to video cassettes and the Internet, pornography has been a key driver of growth. Now, porn is showing up on mobile phones and it's relentlessly wearing down the wireless carrier's bandwidth.

In Japan, where third-generation wireless networks are more pervasive than in the U.S., buffet-style wireless internet access (all you can eat) is causing demand for porn to surge , while putting pressure on margins and on the networks themselves.

Users of Google (GOOG) in China have found themselves unable to access its main site, or its China-based site and services. The apparent reason: the Chinese government is angry with the company for spreading pornography.

"We have found that the English version of Google.com has spread lots of pornographic, lewd and vulgar content, which is in serious violation of Chinese laws and regulations," Qin Gang, China's foreign ministry spokesman, said at a news briefing, the Associated Press reported. Google, he said, was told to remove the porn "immediately."

Porn king Larry Flynt is now an economic pundit.

The founder of Hustler magazine appeared on MSNBC to discuss the efforts of some cash-strapped states to tax pornography. Flynt, who as far as I know is not a member of the libertarian Cato Institute, got straight to the point: "What do they want you to do? Participate in it less?"