Hey, I opted for on online interview this year, but haven't interviewed yet. I could not make it because as an international student I can't get a visa before the interview day. However, I asked my friend who is in a clinical psych phd program and she said that online interview should work as effective as face to face interview. Technically, the admission committee should not jump into the conclusion that you are not interested in this program just because you could not come to the interview. This is what I heard, hopefully someone with real Skype interview experience can answer you question too!