"A few years ago we had concerns about chat rooms and hooking up, but now are turning it on its head and using social networks for educational purposes," Kates said.
Craigslist.org has agreed to add a health message and link to the San Francisco City Clinic site on its "casual encounters" and "men seeking men" pages. AshleyMadison.com also posts an safe sex education forum.
"We became convinced that friends can be good medicine, and if we are able to increase the conversations in social networks about HIV, it can have a positive effect in decreasing the rate of infection," said Steve Morin, director of the Center for AIDS Prevention Studies (CAPS), which also worked with gay.com to post an "Ask Dr. K" forum.
Using the Internet to notify partners is also becoming "standard practice" in public health, according to Morin.
Manhunt.com, with about 4 million active profiles, was the first dating site to address sexual health in 2002 with partner notification, outreach and research services on its Manhunt Cares page. Its directory lists hundreds of health clinics around the world where men can get face-to-face help.
"Manhunt has been an industry leader," said David S. Novak, a former CDC coordinator who heads up Manhunt Cares. "We are hoping to pressure Facebook and MySpace to create health profiles of their own because so many of the infections are with young kids. They can show us up, compete with us."
ISIS, an organization that finds technology solutions for sexual health, sponsors Inspot.org, where those who are HIV positive can send anonymous "e-cards" to notify up to six sex partners in 11 cities and three languages.
"It lets you know if you've been exposed and links you back to testing and resources," said ISIS Executive Director Deb Levine. "The social network mobile community is here to stay. This is not something we can ignore and it will go away. It's very much a part of our lives."
The Chicago's Howard Brown Health Center, where Brett sought help, has created active profiles on numerous sites, such as Facebook, Adam4Adam, Barkackrt and MySpace, to help those who are infected to contact their sexual partners.
The clinic also does proactive outreach on 30 other sites to raise awareness. According to Daniel Polner, the clinic's manager of disease intervention, social networking sites are less anonymous that the traditional venues where gay men gathered.
"In the bathhouses and bookstores the culture is not to ask the name," Polner told ABCNews.com. "But online you have a screen name or a buddy list or, on Craigslist, you can trace a person's e-mails."
"Some people call it anonymous, but it's not," he said. "There's a way to reach the person."
Just this week, in an unrelated incident, police were able to track the suspect in the so-called Craiglist killing in Boston through the e-mails he sent to a masseuse.
"I know it sounds very Pollyanna," said Polner. "But the one thing we always say is, it's not who you meet and where you meet them, it's what you do. The person makes the decision to wear a condom, and in many of those [Internet] situations, they are less likely to be drunk. Whatever their decision, it's more intentional."
Meanwhile, Brett has joined Howard Brown's board, and is taking good care of himself, preferring to make contact with his sex partners the old-fashioned way -- in person.
He still has accounts with gay dating sites, but said, "I don't use it for one night stands, and my profile says 'Do not contact for hook-ups."
"It definitely has become a bathhouse," he said of social networking. "Everyone I know has Manhunt or Adam4Adam, even my friends. It's really sad, even with Facebook, that we go online and meet these people and rely on the Internet rather than engage in person."
"If I meet someone in public, chances are I am with someone who knows something about them and give you a little more information."