There's a point in the movie Time Bandits that goes something like this:
Strutter: Why should we do what you say?
Randall: Do you want to be leader?
Strutter: No. We agreed. No leaders.
Randall: Right. Now shut up and do as I say.
That's sort of the role of the Poobah. Except for the "doing as I say" part.
The Poobah is a term given by Jim Kelly to the person who has to be spokesperson for the workshop, contact prospective new members, push dates and locations for meetings, etc. The current Poobah for CSFW is me, Steven Popkes.
The Poobah is not the leader of CSFW-- no writer I've ever met would ever accept leadership. What the Poobah does is make sure things get done that the group has decided must be done. This can include meetings, inviting of new members or other things.
Other workshops have probably addressed this in different ways. In our case, we did everything by consensus for a few years until the first Poobah, David Smith, decided to start organizing things. He was Poobah for a decade or more and then left the workshop. The workshop decided this role had value and I was asked to step in.
A few years ago I looked up a job out West herding tomcats. Turned out I was overqualified.