I was thinking (at the time) in terms of the live perormance and the'performer' not having to face the audience for whom they are performing the work, and therefore letting themselves get more involved and to go to further extremes (of childishness or seriousness even sexual openness?). I like the jazz improv methaphor used by Damien. For some reason I always think of these peformances in terms of Performance Art, mainly because I always imagine a type of televised performance over distance. Discussion so far has expanded my idea of what these shared performance spaces are/can be, so many thanks to everyone for helping me think one stage further.