I've been doing a few "virtual" presentations lately. We have a lot of requests to present the new features of SQL Server 2008, and I've found that I can go to more places if I do them over the web, using LiveMeeting. It's actually working pretty well. It takes just as much time to get ready on my side, but the participants just log in and watch from wherever they are.
I'm also working with SSWUG to record a series of presentations for their "Virtual SQL Server Conference". It's the same concept, although they are using another viewer. I really like the idea, since it's very inexpensive, it's "green", in that the presenters travel once and the participants don't travel at all, and it's at the participant's convenience.
As long as you give the presentation your full attention, it's tough to see a downside to this approach. Sure, I think that part of the draw of a conference is networking, but there's always TechEd for that. Make sure you check out this kind of format - whether it's the SSWUG offerings or others. I think it's a great idea. You can check out the SSWUG link here: