Arthur, I think it would be a great idea to organise a web conference site powered by mambo to run with the Mamboday expo. That way the whole world could be involved, from a live video feed or two, to online speakers and downloadable videos/pictures and articles from the day.
It would be some undertaking, but I think it would be worth it and could be planned successfully for next year. Web competitions could be run in conjunction with the event, so attendees both in person and virtual could vote on the various challenges (best template done over the weekend for instance).
I'd love to work on such a Mamboday expo site, so if you're interested, so am I
Cheers,
Damian