I just gave a one hour presentation on "How to Create an International Graduate Level Course Using Moodle" to "Moodlemoot Virtual Conference" (MMVC11) via video conference. The video and audio worked fine, but I was not able to get the screen share function to work. So instead I pasted the web address for each slide to the text chat window. As with most such text chat systems, it turns URLs into links, so the participants just needed to click to see the slide. This might be all that is needed in many cases. It has advantages over a screen share, as a smaller amount of data is transmitted. Also it has security advantage, as the participant has to have access to the web page to see it. If an unauthorised person gets into the video conferecne they will still not be able to see the slides.