Jessica Guynn

USA TODAY

Correction and clarification: A previous version of this story had the wrong name for Preferred411.com.

SAN FRANCISCO — For years, sex workers have been the entrepreneurs in Silicon Valley that no one talks about.

But with money flowing from the technology industry, the sex trade is booming.

"I continue to see an increase in the amount of technology clients I see here in the Bay Area," said Siouxsie Q, a 28-year-old sex worker.

Silicon Valley is better known for its search engines and smartphones than it is for sex.

But the sex industry has been closely linked to boom times in the Bay Area going back to the Gold Rush, when men with pickaxes ventured here hoping to hit the mother lode.

"Anytime you have a lot of young men coming West to seek their fortunes, the sex worker industry responds," said Q, who is an activist for sex workers, writes a column for SF Weekly and has a podcast,The Whorecast.

The glare of the national spotlight is on Silicon Valley sex workers after news broke this week that an alleged prostitute is charged with leaving a Google executive to die on his yacht in Santa Cruz, Calif., after shooting him up with heroin.

Forrest Hayes, 51, was found dead last November aboard his 50-foot yacht, Escape. Alix Tichelman, who police say is a high-priced call girl who charged $1,000 to perform sexual acts, is facing manslaughter charges for her role in his death. She is being held on $1.5 million bail.

Police say Tichelman had an "ongoing prostitution relationship" with Hayes that began when she met him on SeekingArrangement.com, a service that says it connects "sugar daddies" with "sugar babies."

FEDS CRACK DOWN

The Internet is rife with anonymous websites that match sex workers with clients and help them avoid being arrested or assaulted.

The websites have both broadened the sex market and helped customers hire prostitutes more discreetly.

Preferred411.com, which bills itself as a "screen service for those who seek only the most discreet experiences in upscale adult companionship" and charges $129 for an annual membership, offers "escort" services in all 50 states, Guam and Washington, D.C.

Scott Cunningham, an associate professor at Baylor University who studies the economics of prostitution, said the Internet has made the sex trade "extraordinarily efficient," taking it from the streets and red-light districts to home computers and smartphones.

Federal authorities have taken notice and started cracking down on Internet-enabled sex.

The FBI recently shut down a Bay Area website that had for a decade operated as a marketplace to connect customers and sex workers.

A grand jury last month indicted Eric Omuro of Mountain View, Calif., and Annmarie Lanoce of Rocklin, Calif., on charges of profiting from MyRedbook.com, which had reviews of escorts and strip clubs, explicit photos of prostitutes and "menus of sexual services."

The website used acronyms to refer to sex acts and sold VIP memberships so customers could access private forums and search reviews of services offered by sex workers.

Prosecutors are seeking to seize $5.4 million they say Omuro earned from the enterprise.

But local police departments say websites advertising escort services are rampant on the Web, and still others will be created to fill the void left by MyRedbook.com. The law generally shields Internet companies from liability for illegal activity taken by people who use their services.

"Before the Internet, clients didn't know where to find the prostitutes and prostitutes did not know where to find the clients. If you think about it in an economic sense, the Internet has removed a lot of the friction from the market," Cunningham said. "And when you reduce search friction, you get a lot more searching and a lot more of that activity."

Unlike British actor Hugh Grant's infamous prostitution arrest, "this Google executive did not have to worry about getting caught," Cunningham said. "Had he not overdosed, no one would have ever known what happened."

SEX INDUSTRY HUB

For decades, Silicon Valley has been a magnet for sex workers looking to strike gold, too.

At the height of the dot-com boom in 1997, the San Jose Mercury News called the technology industry a "prime target for trafficking" because of all the "lonely single men with money to burn."

Last year, a sex worker told CNN she had made "close to $1 million" servicing rich young men. She said she wore T-shirts such as "Winter is coming" and "Geeks make better lovers" to attract them.

"Silicon Valley is like a military base: There are very few civilian women and lots of money," said one Silicon Valley entrepreneur who spoke on the condition of anonymity because of the sensitive nature of the topic.

Q says her clients range in age from 21 to 61. Some are start-up geniuses, others are technology executives. They are all looking for the same thing: a break from demanding jobs, long hours and high stress.

"So much of what my clients pay me for is that both of us turn off our cellphones and we have two to three hours of connecting with another human being that is not through the interface of a screen or phone and has nothing to do with whether someone's stock is going to drop or not," Q said.

TECHNOLOGY AND SEX MAKE GOOD BED PARTNERS

Not only do young tech workers buy sex, sex workers say they use technology to power their businesses.

One sex worker told CNN she uses credit-card payment processor Square to charge clients, a detail borrowed by the HBO series Silicon Valley, which showed a stripper swiping a credit card after dancing for a house full of geeky engineers.

Sgt. Kyle Oki of the San Jose Police Department Human Trafficking Task Force said prostitutes are gravitating to the Internet because they can charge clients they find there more money for the same sex acts.

Technology has also emboldened their clients. Men who might have shied away from buying sex now seek it out on the Internet.

"Now that everyone has a smartphone at their fingertips, men can go on the Internet and don't have to worry about being out in the open," Oki said.

That could be changing.

Q says MyRedbook.com was the most widely used website by sex workers and their clients on the West Coast because it offered free advertising, which helped even the most economically vulnerable sex workers screen potential clients and avoid putting themselves at risk.

Now sex workers have become more fearful of taking on new clients without any way to check their backgrounds. Some are even referring to it as the "Hooker-pocalypse."

"With MyRedbook's FBI shutdown, sex workers are definitely financially struggling," said Kitty Stryker, a former escort and media manager for TroubleFilms, a gay and lesbian porn company. "I think any possibility of the current tech boom trickling down to sex workers is limited, partially because clients are afraid of the FBI now, and partially because they can't find our ads. I personally have turned to porn as a more consistent option."

Contributing: Donna Leinwand Leger