And crackdowns that big are raising fears that authorities could be renewing their focus on the escort business.
"I think right now [sex workers] are a huge target because there has been a lot more pressure from various conservative organizations," said Sabrina Morgan, a rights advocate for the sex worker industry. "This is something that has been building steam for several years."
Read MoreJapan's celibacy issue—What's the economic cost?
Today's escorts rely on sites like MyRedBook and The Erotic Review, which receives 500,000 to 1 million unique visitors per month, to raise awareness and advertise their services. Eros, for example, charges anywhere from $100-$400 for escorts to run an ad, depending on location.
In addition, many escorts have their own promotional Web pages where prospective clients can learn more about them and set up appointments. For those sex workers who do not have Web design skills, there are several online services—like EscortDesign and EscortBook—that, much like WordPress, offer easy-to-create templates which can create a professional looking site in minutes.
That gives sex workers who advertise their services online more independence, too. Ninety-three percent of Web-based escorts classify themselves as "independent," compared with the 40 to 80 percent of street walkers who work under a pimp, says Cunningham.
And the more sophisticated and well-designed an escort's site is, the more it helps their bottom line.
"If a prostitute invests in her web site's copy editing, professional photographs, or video, this may signal to potential customers her quality, education level, or income (and thus popularity or success in the market)," University of Colorado law professor Scott R. Peppet said in a research paper. "Such signals matter: evidence suggests, for example, that sex workers proficient in English can charge higher prices and are more likely to attract customers, and that prostitutes willing to reveal an accurate picture of themselves command higher prices."
— By Chris Morris, special to CNBC