Meant to post this yesterday - too busy, and probably wont get round to finishing it so here goes:
"Talk of a 'definition' is meaningless."
Apparently not, to some people anyway Howard – that's why there have been so many of these threads
I have no problem with a definition – I have one that works or me and I'm happy to stand by it, flawed as it may be.
Folk songs have been created and proliferated by working people down the ages as entertainment and as ways of setting down experiences and emotions; they are an essential part of our cultural and social history.
The universality of their themes has enabled them to spread throughout the English/Spanish/Danish.... (whatever) speaking world, be taken up adapted by others – it has also enabled them to be passed on from age to age and serve later generations.
Every single definition has referred to their roots and their being passed on, along with lore and custom.
For me, their long-term importance lies in the fact that they are the creative artifacts of a working people – a social grouping that is largely considered to have no culture of its own.
On a more personal note, my family probably originated in Ireland – they were driven out in the middle of the 19th century by 'The Great Hunger' – there is a huge song repertoire about those times and events – the second largest genre of songs in Ireland, mostly made by those affected.
Those of my family who stayed were part of the resistance to the evictions that took place following the Famine – another large repertoire of songs about those events      
Another large body of songs were created during The Irish War of Independence – another part of my family history – songs of this and the previous type will form an important part to our collection, when it goes up on site next month.
My Grandfather was a merchant seaman who sailed under sail, with a small repertoire of shanties (not enough for him to consider himself a singer) - sea songs make up an extremely important part of our folk repertoire and my family history.
My father was a reluctant navvy – he didn't have any songs, but he had wonderful stories of life on the roads which give me and others a great way into singing songs about navvying.
I have little doubt that there are many others here who can relate to the folk repertoire in the way I find myself able to do, from different parts of the country and different backgrounds – that is the importance of folk song for me – it helps me understand where I come from – it does it for me as a singer and a researcher, I don't know any other artistic form that does that- certainly not pop, or pop based songs.
That's what the folk clubs did for me – take away the intimacy and turn them over to stars with expensive instruments, or shift them to concert venues and festivals, or open them up to marketed pop music and you remove the democracy that the folk revival gave us.   
That's why I'm prepared to argue the toss about what 'folk song' means
Jim Carroll