June 16, 2007 -- An estimated 40 million Americans use online dating services hoping to meet "the one." There are more than 1,400 Web sites in the $700 million a year business, but some question their safety.
Prosecutors say a Philadelphia nursing student was conning women on match.com. He was convicted this week of assault, but the accusations don't end there. His victims, described as attractive, ambitious professionals say their lives will never be the same.
Prosecutors said Jeffrey Marsalis, 34, told some tall tales, pretending to be a doctor, an astronaut and even a spy to lure women on Internet dating sites.
"He faces up to 20 years in prison and he will have to register as a sexual offender for the rest of his life," said prosecutor Joe Khan.
Marsalis was convicted of sexual assault. However, he was acquitted of more serious charges that he drugged and then raped seven women in his apartment.
"You read about it, you see it on TV but you just don't think it can happen to you," one anonymous victim said.
She said she knows about tricksters like Jeffrey Marsalis and how easy it is to be duped online. According to her, a man she met on a Christian dating Web site was seeing 60 other women from 25 different Web sites. He pretended to be everything from a country music manager to a Pentagon consultant. He even lied about having cancer, she said.
She claims he stole thousands of dollars from his victims.
"Mentally, it just about broke me to think that I had been so naive, when I don't consider myself to be a very naive person," she said. "And of course, I was worried about my safety."
She may have good reason to be. Dozens of Internet dating cases have ended in tragedy. And experts said it's only getting worse.
"Men especially are getting are getting bolder as far as using dating Web sites to find their next victim," said Jayne Hitchcock, who is working to halt online abuse.
Experts say potential daters should get to know the person as well as she can before the first meeting.
Meet in a public place and arrive separately.
Let the relationship grow slowly.
Most importantly, trust your instincts.
"Most of these women will tell you that they had a bad feeling about it but they went ahead with it because the person the man had a wonderful profile," Hitchcock said. "He was charming."
One victim said it was loneliness that clouded her judgment.
"Victims are victims because somebody is looking to exploit their weakness," she said. "And it doesn't matter if you're doctor. It doesn't matter if you're an accountant."
She said she wants women to trust their instincts because she didn't trust her own.
About 20 percent of daters admit they lie about themselves online, according to a survey research study by Jeana Frost of Boston University and the Massachusetts Institute of Technology.
But there are a growing number of security tools.
True.com provides criminal and marital background checks, but it's the only site.
Match.com gives free temporary phone numbers to keep your real phone number a secret.
Intelius.com will conduct dating background checks for any dating Web site.
In the Marsalis case, Match.com did not return ABC News' e-mails or calls.