Of the two most successful clubs that I visit regularly, one has the stage in the middle and the other at the end. I don't think it makes much of a difference really - as long as you it's understood by all concerned that the back of the room is not an area for hanging out and talking, so you can still hear the performers back there.

I can entirely see the logic of putting the stage in the middle, but for some reason clubs don't always like to do that, or constantly try different arrangements from one week/month to the next.

No, I don't know why either...

Anahata