Video conferencing is very useful when there is a lot of data going from you to the audience. Proper training which involves interacting and involving all the senses is not feasible over video conferencing.

It is great when you have to explain some technical details, say for an hour, and want to go over the content in a specific pace and let the delegates ask you questions.

The biggest problem in video conferencing is much like voice conference, only one person can talk at a time. The artificiality of this causes people to hold back and the pace is usually very slow.

Overall its just another tool in the toolbox for specific needs.

If you are to use this medium for any kind of developmental work, you should likely focus on 'presenting' information rather than training per se.

As mentioned previously, it is a lot harder to provide the inclusive and interactive approach that true training requires.

Having said that, there may well be some specific activities that you could plan out to work with video conferencing. For instance, you could open the session and give an overview of what you intend to provide development on, then ask each set of people on the video conference to go away and work on a specific task or activity and then pre-arrange a time to continue the VC at which point they feedback their findings. You then set another task etc. etc.

It's one approach that could work, just off the top of my head.