Google shows about 243,000 hits for the "webinar" search term. Clearly it has caught on. But why? What makes the presentation delivery mechanism so special that it has to be embedded into the generic name for the event? What do you call a presentation that is delivered both live in person and over a computer network? Or perhaps simultaneously broadcast over two different mediums? (Oh right, that's called simulcast.)
I suspect that eventually people will remember that the medium is not the message, and we can return to calling presentations presentations. The word "webinar" will be relegated to just another entry in dictionaries of obsolete computer terms.