I naïvely assumed it would be like a presentation but without the visible hand-waving, but it isn't really. For a start, you can't easily poll the audience to find out what their level of experience is, and taking questions is quite tricky, even with the technology to support it. Also, because you're not standing in front of people, I think the "rules" around making sure your slides don't distract from you are a little different - it strikes me that webinars are more like a set of slides with a narrator and a fixed time, than a presenter with a set of slides to emphasise points. This puts the medium in an awkward position between an infodeck and a talk (yes, I am reading Presentation Patterns at the moment, and it's making me very conscious of all my slides and presentations). So my slides are more info-heavy than my usual style.
I actually learnt a lot while I was putting together this webinar, so whether you're completely new to NoSQL/MongoDB, or just starting to use it from a language running on the JVM, it's worth checking out.
(Or see the webinar and slides together)
As always, feedback very much appreciated - I think there's great material in here, but I already have some ideas for improvement.