Thank you everyone for your answers to this question! This is some great, specific feedback that we'll definitely be able to share with future supervisors. It sounds as though Skype/Moodle/Collaborate online "face to face" conversations you found allow for more topics to be discussed at once, more questions to be asked and more of a back and forth dialogue. The recommendation that such a conversation be set up at critical times is quite helpful and makes quite a bit of sense. Thomas, I also really like your comment about having the session scheduled in Moodle, or whichever program that degree uses. That helps with organizing schedules, navigating different time zones and helps with reminders when many online students are also working, have family commitments etc. Many of you spoke of the technological or time zone challenges this form of communication has and mentioned that email can be a great form of communication that negates having to meet at the same time for a conversation. You also mentioned that email may be preferable when there is only one topic/question for the supervisor.
That trust in the relationship sounds even more important when communicating via email as the student is depending on the supervisor to trust they have read the question and are either writing back or looking further into the question before replying.
Thanks for the great comments on this thread!