I used to do this quite a bit, back when I had just started my practice and was building up my caseload. Then two things happened: I got busy, I began to experience problems with my connection to the internet.
My internet connection was fine for email and web pages, and the like, but Skype uses a great deal of data. It would slow down or shut down at inopportune times; not the thing you want to have happen in the middle of a delicate therapy session. Therefore, I stopped seeing clients over Skype.
Then someone who had been seeing me face-to-face began to travel a lot on business. She asked about Skype sessions. I looked into it and found that another service, etherapi.com, was tailor made for video counseling. It relies on a low bandwidth transmission that does not strain my connections the way Skype does. Not a lot of detail, but plenty for counseling. They also pay close attention to the privacy needs of therapists and their clients.
Consequently, I now offer video counseling in my array of services. Click here if you would like more information.