The promise of videoconferencing in the 90’s and online conferences since then has fallen well short of expectations.
The simple fact is that face-to-face communication is the single most effective means of communicating. A former client of mine had a situation a couple of years ago where they had two phone briefings with a prominent analyst. The calls went extremely well but when they met with him face-to-face a month later, he wanted to know what they did!
Where online events do hold the upper hand is in cost-effectively reaching a larger number of people and of course reaching people unable to make a physical event.
Of course online events require a lot of preparation and a lot of promotion. Channel Seven have an excellent article looking at online events and what makes them successful.