I confess that I've not read all of the contributions to this thread but I've not yet seen any mention of the late, great Ewan MacColl, who, together with Alan Lomax and Bert Lloyd was one of the architects of the Folk Club movement in the UK. In fact many commentators believe that the first Folk Club was 'The Ballads and Blues Club' founded by these three remarkable men, in the early 1950s, in London (and I won't be surprised if dozens of people queue up to dispute this - anti-MacColl prejudice is still going strong 17 years after his death).

There is a fascinating, if highly speculative, paper in the recent publication 'Folk Song, Tradition, Revival and Re-Creation' edited by Ian Russell and David Atkinson, pub. The Elphinstone Institute, University of Aberdeen, 2004 (ISBN 0-9545682-0-6). The paper is called, 'Folk club or epic theatre: Brecht's influence on the performance practice of Ewan MacColl' by Michael Verrier. This suggests that, in creating the folk club format, MacColl drew on his knowledge of theatrical techniques to evolve this format, particularly those now associated with the German playwright, Bertolt Brecht.
The paper discusses why this may be important and, if you're interested, I invite you to read it for yourself (there's not a lot of point in me trying to summarise it). Nevertheless, I can't resist quoting the last line of the paper:

"...if the folk club is seen as epic theatre, then MacColl wrote the script for a play that is performed with infinite variation in a multitude of venues every day."

If it's true, then that's quite an achievement!