Research has established the efficacy of online therapy with treatment outcomes at least equal to traditional in-office, face-to-face setting [e.g. Barak, A., Hen, L., Boniel-Nissim, M., & Shapira, N. A. (2008)].
Other related research concerning online therapy:
Cohen, G.E.; Kerr, B.A. (1998). Computer-mediated counseling: An empirical study of a new mental health treatment. Computers in Human Services 15, 13–26.