The conventional wisdom is that purveyors of pornography do well in soft economies. When people are unemployed and high gas prices make travel and dinners out expensive, many men choose to stay home with a good book and a pretty girl.

But that hasn't been the case lately. In this weak economy, pornography stocks have been terrible performers. Playboy (NYSE: PLA) reported lousy first quarter results, and its stock has taken a beating so far this year. Shares of New Frontier Media (NASDAQ: NOOF) are down nearly 30% today after that company reported lackluster fourth quarter and full-year results.

So what gives? Have men lost their appetite for pornography, and are now spending their free time doing crosswords and watching The Discovery Channel?

According to USA Today, amateur pornographers armed with little more than a webcam and a computer are giving the major players in the adult entertainment industry, like New Frontier Media (NASDAQ: NOOF) and Playboy (NYSE: PLA) a run for their money.

Sales and rentals of adult DVDs have plummeted in recent years, and now sites like PornoTube.com and YouPorn.com (such clever names ... not) are allowing consumers to download user-generated content to their computers, and even cell phones ... for free in most cases.

While the big porn companies have been pretty quick to move onto the internet, replacing DVD sales, you have to wonder how much user-generated content will hurt their sales. Is Playboy delivering a product that much better than some of the amateurs on PornoTube? I wouldn't know because I'm a good boy.

Shares of Playboy and New Frontier have performed poorly over the past few years, and you have to wonder: How much does branding really matter in an industry that is now flooded with free content?

The market doesn't appear to be giving Playboy a lot of credit for the brand it's been building for the past 54 years: The stocks trades with a market cap of $365 million, which is about 1 times sales. If the brand does still have value, it could be ripe for a buyout -- but only if that's what Hef wants.

Last week, for the first time ever, Chinese men had a chance for that once-a-year spectacle that so many American men have counted on for decades: the Sports Illustrated swimsuit edition. While pornography is still outlawed by the communist government, it's a wall that appears to be on its way down. Soft-core pornography is becoming more available, and some websites are going even further.

It seems likely that as China continues it's sprint toward modernization, pornography will one day be legal there. When that happens, the adult entertainment industry will gain access to a huge new market. I would continue to monitor China's laws and, in the event that pornography is legalized, take a long look at stocks like Playboy Enterprises (NYSE:PLA) and New Frontier Media (NASDAQ:NOOF).

Of these two companies, New Frontier has been performing far better of late. But an iconic American brand like Playboy may find new life in China, where all things American (like baseball) are the rage.