The reason there were two microphones moving around was because the wired microphone cables were taped down so tightly that there wasn't enough play to use just one. I had tried to explain to people how to make this work in "serpentine" fashion (and Lisa was expecting to record it that way), but as you see, people don't listen very well. About the only way this will really work is when there is one, wireless microphone (or someone holding a microphone and carrying it from person to person) and an individual directing people.
There is a practical reason for doing this video: it's one of the ways we can clearly identify who are in the Worldcon Chair photos. Scoff if you like, but I know from painful experience that looking back at the old photos, we can't always tell who was in them.