I moderated a panel discussion on Information Architecture in Second Life at the IA Summit in March. It was a joint Real Life/Second Life event, and it worked rather well.
The technical objective was to enable conference attendees on the Real Life (RL) side to hear and see panelists on the Second Life (SL) side, and for panelists on both sides to at least hear each other and the audience. In other words, we needed the minimum conditions for panelists and audience to talk with each other, regardless of their physical location.
We accomplished this via a Skype conference call and a Second Life connection through a laptop in the room. The audio was amplified from the RL laptop through the room's sound system; the Second Life connection was shared with the room through a video feed from the RL laptop to the projection screen; and audio from the room to the remote participants was managed via the mic in the RL laptop. Also, the remote panelists and the panelist running the RL laptop all logged into Second Life and met at Info Architecture island. During the discussion a number of members of the audience logged into Second Life as well and joined the others at Info Architecture isle.
During a trial run we'd also managed a direct visual hookup between RL and remote panelists through Skype via the webcams in the participants' laptops. This caused a lot of lag, while affording remote panelists only a narrow view of the first few rows of seats, so we omitted this channel during the event.
This low-tech solution required no streaming audio or video server, which is good. However it was dependent upon the ad-hoc audio from the room being good enough for remote panelists to hear... which fortunately it was. And because there was no video feed from the RL room, remote panelists were blind to what was going on in the room. This setup was centered on the physical location of the conference, and would not enable people to participate as members of the audience from Second Life only.
Participating from Second Life were Beth Kavka (Beth Kanter) and Lori Bell (Lorelei Junot). Present on the Real Life side were Josh Knauer (Hayduke Ebisu, who also managed the technical arrangements and ran RL laptop), Andrew Hinton (Banjo Quonset), Sarah Dilling (Sally Linden), and myself, Stacy Surla (Stacy Narayan).
For a look at what we actually discussed, read Beth Kavka's blog entry about the session, or see the Information Architecture in Second Life (Redux) slideshow.