I spoke at the University of Kansas the other day. Kansas is far away so I gave the talk by video. We did it using a G+ hangout, and it worked really well, much much better than when I gave a talk via Skype. With G+, I could see and hear the audience clearly, and they could hear me just fine while seeing my slides (or my face, I went back and forth). Not as good as a live presentation but pretty good, considering.
P.S. And here’s how to do it!
Conflict of interest disclaimer: I was paid by Google last year to give a short course.