Let me suggest a naughty idea:
A lot of people would like to see some of their friends naked. A lot of people would post nude pictures online if the price is right. Therefore, consider the new site, D***Starter.
Find your friend, and anonymously donate to their DStarter project. When others donate to the same project, and the pot gets large enough, your friend can withdraw the cash by posting a nude picture publically online. It's like KickStarter, but instead of projects, you're funding nude pictures by particular people.
Social disgust is the biggest barrier to making this site work. But if you keep donors anonymous, social pressures shouldn't be enough to keep private donations from occurring.
The other side of the coin from social disgust toward funders is social disgust toward the funded; the people stripping for cash. But this just makes the price to strip need to be higher before they'll do it. I suppose many thousands of dollars would be required to pay for the embarrassment of posting nudes, and perhaps many more thousands to pay for the negative social judgement. But the question is, is there a price? I suspect for most people there is some price at which they would sell the revelation of their body.
You might call it selling your integrity, but your integrity was always for sale, the site just reveals the price.
May I also suggest that the site may reduce the prevalence of rape. Porn is a substitute for sexual crimes, and porn of someone you know is a closer substitute for a sexual crime toward that same person. After all, most rape cases occur by people the victim knows.
Regardless of the morality of the issue, on which I take no stand, it seems like a profitable business venture. If someone only has the gumption to do it.
Another somewhat related idea I had is the People rating App, Yelp for people. Though it seems others have already addressed the idea in the form of an actual low-rated Application and a fictional dystopian future. Unlike D***Starter, I think Yelp for People would probably be a very good idea for society, and the fictional dystopian future is ridiculous satire that shouldn't be taken seriously.
So between these two ideas, why don't they exist? Why aren't they popular? What hasn't the efficient market hypothesis brought them to life? One reason might be that the public has a moral distaste for both ideas. If you invent either you're going to get a serious knock on your social rating (the invisible social rating that Yelp for People would state in more clear terms). Most people care a lot about where they stand in the eyes of others, so in some sense it might be financially profitable but socially expensive product to create.
But all it takes is one person somewhere with strange values and an interesting idea to get all of us to rank each other out of five stars and post naked pictures publically.
Oh man, and Merry Christmas!