I wrote 'articulated' by its practitioners, not labelled.
'Folk' is not a label - it defines the music; it refers to its origins, it's creation, transmission, its function and the people it served.
Exclude tomatoes from soup and it ceases to be tomato soup, take folk out of folk music and it ceases to be folk music, no matter how many people wish it were otherwise.
Tom says his particular tin is labelled 'Story songs', which could place it in the 'opera', 'country and western' or 'music hall larder; it has no part in the overall definition.
Wikepedia includes 'electric folk' in its definition, yet does not include Vaughan Williams or George Butterworth or Percy Grainger, who all have a greater claim to the source of the music. If you are going to widen your definition, surely you must remove all the boundaries.   
Incidentally, at the 1971 Loughborough Folk Festival, one of the leading exponents of 'electric folk' Bob Pegg astounded a roomful of people by announcing that he was no longer interested in folk music. When asked why he still played it, he replied "for the money".
Jim Carroll