The quirkiness of Internet connections can also be an impediment. “You have to prepare vulnerable people for the possibility that just when they are saying something that’s difficult, the screen can go blank,” said DeeAnna Merz Nagel, a psychotherapist licensed in New Jersey and New York. “So I always say, ‘I will never disconnect from you online on purpose.’ You make arrangements ahead of time to call each other if that happens.”

Still, opportunities for exploitation, especially by those with sketchy credentials, are rife. Solo providers who hang out virtual shingles are a growing phenomenon. In the Wild Web West, one site sponsored a contest asking readers to post why they would seek therapy; the person with the most popular answer would receive six months of free treatment. When the blogosphere erupted with outrage from patients and professionals alike, the site quickly made the applications private.

Other questions abound. How should insurance reimburse online therapy? Is the therapist complying with licensing laws that govern practice in different states? Are videoconferencing sessions recorded? Hack-proof?

Another draw and danger of online therapy: anonymity. Many people avoid treatment for reasons of shame or privacy. Some online therapists do not require patients to fully identify themselves. What if those patients have breakdowns? How can the therapist get emergency help to an anonymous patient? “A lot of patients start therapy and feel worse before they feel better,” noted Marlene M. Maheu, founder of the TeleMental Health Institute, which trains providers and who has served on task forces to address these questions. “It’s more complex than people imagine. A provider’s Web site may say, ‘I won’t deal with patients who are feeling suicidal.’ But it’s our job to assess patients, not to ask them to self-diagnose.” She practices online therapy, but advocates consumer protections and rigorous training of therapists.

Psychologists say certain conditions might be well-suited for treatment online, including agoraphobia, anxiety, depression and obsessive-compulsive disorder. Some doctors suggest that Internet addiction or other addictive behaviors could be treated through videoconferencing.

Others disagree. As one doctor said, “If I’m treating an alcoholic, I can’t smell his breath over Skype.”