From KAREN wiki

At The University of Waikato, most use of videoconferencing rooms to date has been for meetings or to make a presentation being given on site visible to an audience elsewhere.

But videoconferencing rooms can also be used the other way around. For example, in May 2009 Dr. Peter Komisarczuk (at right) of Victoria University's School of Engineering and Computer Sciences was among those providing lectures for a University of Waikato graduate Computer Science course. Dr. Komisarczuk described work undertaken by him and others on the detection of malicious Internet traffic and analysis of the way in which malicious web sites behave. For more information, see http://ecs.victoria.ac.nz/Main/ResearchSpotlightOnHoneypots

Including teaching by outside speakers allows students, especially at graduate level, to be exposed to a much wider range of research than would otherwise be possible, and gives them a better appreciation of the breadth of their subject.

Using videoconferencing rather than recorded lectures means lecturers can see the reactions of their audience, and students are able to ask questions in the same way they would were all participants in the same room.

And it's a great easier to give a lecture from a room at your home institution - perhaps literally from your office - than to travel to where interested students may be.