I work for a software company (Motionsoft) and we have a lot of clientele who use online personal training. The type of people who use them are generally self-motivated, and don’t need someone in their face to get the workout done. They are typically full-time worker’s who workout on their own time, or whenever they have free-time. The key is being able to make sure you effectively communicate the workout, just as Harris stated above. Stay on top of them and make sure you keep them motivated, because as you can expect, it’s alot harder to motivate people using an online PT.
Hope this helps,