"This is perhaps why we have problems defining it. "
Up to farly recently definition hasn't been a problem - this really is a new kid on the block as far as us veterans are concerned
This cultural self-imposed myopia started with a revival that had apparently become bored with the traditional repertoire and wished to encompass other genres in their 'folk club' evenings; nothing wrong with that if you had audiences who liked big ballads and Victorian tear jerkers'.

As a frequent visitor to fok clubs in the sixties and seventies I was for a time prepared to listen to all sorts, within reason, but eventually it came to the situation that you often went home from a folk club without hearing a folk song.
I stopped going to clubs and so did many thousands of other folk song lovers - the ccene took a nose dive and hundreds of clubs disappeared - as did those who had formerly attended them
The folk venues had transmogrified into something we, as individuals, could no longer put a name to.
Unfortunately, the organisers continued to (often very aggressively) continued to call their clubs 'folk' - there had been a hostile takeover of our 'Other Music'

Those of us who continued to expect to heat folk songs at folk cubs were called 'Folk Police' or 'Folk Fascists' or 'Purists' or 'Finger-in-Ear'
We have now reached the stage that, on a forum that claims to be about "Traditional Music and Folklore Collection" we cannot discuss folk song definition - it has become a no-go area

We have a workable definition; as flawed as it mat be it is a reasonable rule-of-thumb to our music - "54" has become a term of abuse and contempt
Instead of repairing the flaws, any attempt at defining it has been totally abandoned - it has become a music without a name, "unless you accept "singing horse music" (based an an apocryphally-credited old joke)

Our music is as well-researched and documented as any other, possibly better
I have many hundreds of books discussing the features and peculiarities of folk song, lore, narratives, dance music.... (all related disciplines)
Up to the eighties, folk song had its own clear identity which was reflected in clubs, records, literature, shops full of goods... (an entire cultural and at times, thriving movement)
Now it a "dog and a cane and a bell" to identify it.

I fell under the influence of Ewan MacColl's singing in the early 1960s - later, when I got to know him, I fell under the influence of his ideas on folk song
In the early days he would insist that whatever happened folk song would never die.
Pat and I carried out an extended six month interview with him in the early 1980s - by then he had adapted to "Folk song will only die if it falls into the hands of people who don't like or understand it" - I'll drink to that never happening every time

Significantly MacColl is another no go area on this "Traditional Music and Folklore Collection" forum, and if things go on as they are, so will Child and Sharp and Lloyd and Lomax...... and all those dedicated and talented visionaries who gave us this wonderful cultural phenomenon
I hope I'm not around to witness that particular book-burning

When you say there is a problem defining folk song - please spaek for yourself - some of us don't have that problem
Jim Carroll