According to PhysOrg.com, Cognitive behaviour therapy (CBT) via the internet is just as effective in treating panic disorder (recurring panic attacks) as traditional group-based CBT. It is also efficacious in the treatment of mild and moderate depression. This according to a new doctoral thesis soon to be presented at Karolinska Institutet, Sweden.
As a therapist, I find internet therapy to be valuable but limited. There is really no substitute for face to face interaction. MoodGym is an excellent source for online CBT. However, it is more educational than therapeutic. In this online age, there may be people who prefer online therapy, but I still maintain that it is less efficient than conversing with a trained professional.