But each night, she walked away with peanuts. So when she met a gangster who said he'd pimp her and make her thousands more—to go on easy dates, and just give the experience of a girlfriend—Kate fell in love with the idea.

He took her to a room and made her do shi gong, a Chinese term for trying out the girl before you sell her. Then, he left Kate in the lurch.

This isn't the plot of a 70s triad film—it's just one of many typical examples of why young sex workers in the city are using technology to work for themselves. Soon after Kate ran into trouble at the nightclub—like many other fresh-faced high school girls in Hong Kong today—she discovered online forums to run her own business as a sex worker. On HK Big Man and HK Mensa, where ads are proliferating everyday, so-called "compensated daters" offer their services without the help of a middleman.