Got to do an open mic last night with Frank. I noticed a couple things that tend to happen when the microphone is shared throughout a night.
1.) audience gets involved, spontaneous performances occur
2.) lots of support, musicians support other musicians. Since there are performers from all levels there is a great degree of acceptance. We accept beginners just like we accept experts.
3.) The venue becomes communal when people agree to share the microphone/spotlight. More voices, people are happy to be heard.