Broadly speaking,50% of the inhabitants here think that folk songs are a particular kind of song, defined by usage and/or creation in some sort of communal context, which leads to songs existing in many variant forms.
Another group thinks the category also includes songs written by people with guitars (and probably long hair) since the 60's (these songs often deal with the writer's personal emotional life and problems in some detail).
Another group admits various other kinds of popular songs into the category (hence Dire Straits etc).
Then there is a small subgroup, consisting of Big Bill Broonzy, Louis Armstrong and McGrath from Harlow, who believe "all music is folk-music, leastways I ain't never heard no horse sing a song". There are no horses, as far as I know, who are Mudcat members, otherwise you might find even more extreme positions being taken. .