Sorry to be a pain (well, I'm not sorry really!) but definitions ARE important. How on earth can we answer a question like "How much Folk Music is there?" if we don't know what folk music is?
I've never been happy with this idea that if you label/define something you somehow diminish it. Just as a 'non-folk' example of why this attitude is wrong, at this moment in history we appear to be losing thousands of species from the biosphere and not being able to identify/name them will contribute nothing, whatsoever, to saving them from extintion.

I also suspect that those who insist that there is no acceptable defintion of folk song/music (in the face of the highly authorative and convincing IFMC definition, for example) are guilty of mis-direction for their own purposes. In the Introduction to the new publication, 'The Folk Handbook' (Backbeat, 2007) Vic Gammon writes, "It [the post-war Folk Revival]also produced some unexpected spin-offs, including a whole group of comedians who honed their craft in folk clubs, ...". My belief is that people like these comedians benefited from the lack of widely accepted definitions within the Revival because folk clubs were the most accessible platform for their ambitions at the time. It was in their interest (and the interest of other ambitious but marginal performers) to spread the idea that "all music is folk music' and that, therefore, 'anything goes in a folk club'. Sadly, this pernicious myth lives on and is oft-repeated - all too often on this board ...