I've remotely presented to New Zealand via webcam streamed into Second Life and would be happy to do something. Unless there were a heap of avs also in SL, or a mike or wireless keyboard in the crowd, it *might* be a bit "sage on the stage" for an unconf.
Why don't you contact Elluminate and see if they would be willing to use their web conferencing to help with this? They've been active at a number of conferences recently e.g see ALTC 2008 for what they did there. That would have the added benefit of post event recordings too.
OK, as this all gets a bit more concrete, I'm trying to firm up details. If you are interested in remote participation, can you leave some suggestions here of what you would want to be able to do? Is it just an official 'comms' channel. Do you want to hear/see what is going on?
I'm not sure what is possible at the moment, but I'm also not sure what people want to be able to do...