Hi Paul, I agree with your comment about the use of video, particularly in platforms like Elluminate. I usually limit the presenters use of video in Elluminate to just prior to the presentation. One presenter from the Open University did give us a very short walking tour of his offices which was fun in that it was new, but really, it's just offices.
The best use of video in conferences that I have heard of has been by the Supporting Deaf People Online Conference. Video was used to enable signing between deaf people and the professionals who support them. The conference delegates were from all over the world. It's a great example of how online conferencing provides accessibility to conferences and connects people who otherwise would not be able to meet.