Having participated on a few sessions at CodeGear's online CodeRage conference, I can only say that this is a very good way to make conferences. There are lots of advantages over a traditional conference and the costs are much lower. You can chat with other attendees during a session, asking questions, you can leave the session without disturbing if it gets too boring, and you can do other work if the topic is easy for you. On the downside, you don't get those extra days in a geographically remote location and you don't get the beers afterwards, but I guess we'll see this evolve a lot in the coming years. Unfortunately, there's also the downside that CodeRage was arranged for U.S. time, meaning that it's after business hours in Denmark.
However, I can only recommend to sign up and participate in this kind of conferences.