"These sites are a great temptation for those who suffer from sexual addiction," said Dr. Kristen Ries, an infectious disease specialist from University of Utah Hospitals and Clinics. "I am especially worried about some of the younger generations who are so Internet savvy, but who seem nonchalant about the seriousness of HIV/AIDS."
"Remember that HIV positive people who are in denial about their HIV, or who are fearful of abandonment if they disclose their HIV positive status, are more apt to seek anonymous sex at such sites," she told ABCNews.com.
With that in mind, many public health agencies are using the Internet to change people's attitudes and educate them about the possible dangers of risky sex.
Some studies have not found the Internet to be inherently more dangerous than bars and dance clubs.
"We haven't seen a huge difference in the risk when sexual partners] are recruited in online rather than other venues," said Greg Rebchook, a researcher at CAPS.
But the center acknowledges that using the Internet to meet sexual partners "creates an environment" where high-risk and low-risk sexual partnering occurs and can increase the transmission of HIV.
Blacks and Latinos account for the largest numbers of new infections (45 percent and 17 percent respectively), according to the CDC, which suggests the cultural shame associated with homosexuality prevents them from seeking or disclosing their status.
"Men who want high risk sex will find it, especially in an urban environment, whether they do so face to face or online," said Dr. Demetre Daskalakis, founder of the Men's Sexual Health Project at New York University.
"Rather than demonize social networking sites as drivers of the epidemic, we should look more to the root causes of homophobia and hate that generate shame and self-destructive behavior."
After Brett's reckless encounter, he and his friend found Chicago's Howard Brown Health Center online and arranged for free testing. Both are now undergoing treatment.
"I think finding out you are HIV positive makes you grow up a lot faster," said Brett, who graduates with a degree in interior design from Chicago's Harrington School in May.
"A lot of people don't like to use protection," he said. "Some people think if, 'I don't know about it, fine.' But once I found out I was positive, you make sure that you are using protection all the time, and I make sure my friends are."
Public health professionals are turning to social networks as a tool to combat the high numbers of HIV/AIDS infection.
"The whole idea of preventing HIV/AIDS is getting ahead of it," said Jen Kates, vice president of HIV policy for the Kaiser Family Foundation, which is using the Internet to bring more attention to HIV/AIDS. "You anticipate the forums where people meet."
Kaiser worked with MTV's 24-hour college network to develop "Poz or Not," an online game that challenges stereotypes and breaks down the barriers that may prevent people from talking openly about HIV/AIDS, getting tested and using protection.
The "GYT" (Get Yourself Tested) campaign was created under a partnership with MTV, the Planned Parenthood Federation of America, CDC and others to increase testing for those under 25, using a Facebook application.