"No amount of specialist wishing or insisting will make the latter "misuses" go away. "
The general public don't have a single definition - folk music has passed them by.
There was a (sort of) definition at the time of the 'folk boom' largely based on 'the real thing' as presented by the folk superstars - The Clancys, Dubliners, Spinners....
Dylan, in the early days, based much of what he did on 'the real thing' - but he walked away from that and became a born-again rock performer.
In the early days, the media, certainly in the form of radio, had a pretty clear veiw of what constituted "folk" - Lloyd, Deben Bhattacharya, John Levy.... produced some of the finest examples of folk music ever to be publicly broadcast.... the media walked away from it and the term "folk" has become meaningless to them as it has in the "folk" clubs.
You can't 'wish' or manipulate a definition into existence into being to suit yourself - one has to evolve through popularisation or constant misuse by a significant enough number of people for it to pass into common currency - hasn't happened.
What has happened is that a small and dwindling group of people have decided to hang their hat on a hook that is already occupied because they either can't or can't be bothered to create a term that covers what they do.
Personally, I walked away from the folk clubs when I stopped hearing folk songs - no reason to hang around when they all turned into lucky dips and magical mystery tours.
If I want to check what the term 'folk' means I only have to pull down one of several hundred books from the shelf, or dig around sites like 'The Library of Congress' (far more succinct and satisfying than anything ever produced in Britain, as I am finding at the present time).
So far - nobody has come up with an alternative, so what is happening today is that there are efforts by an extremely small,agenda-driven group of people not to re-define 'folk' but to de-define it - to make it meaningless - as has been stated here "whatever else sounds sort of like it - as long as it isn't classical" - this is cultural vandalism.
It has always been accepted that there are a unique group of songs that have been identified as 'folk' (in the case of song, since at least 1899).            
In my opinion, based of forty years of questioning field singers, these songs have a social, cultural and historical significance to our culture as a whole - "The Songs of the People" - "The Voice of the People" - "The Common Muse".... whatever term you care to choose - take your pick.
In making the term meaningless, you stand to marginalise and eventually silence that voice - and in doing so you take away a significant piece of our oral history.
If you are going to do that, you should at least have the common decency to come up with an alternative definition - "folk is whatever I choose to call it" really doesn't hack it.
Sorry to be such a bore
One more thing - Irish instrumental traditional/folk music is at present enjoying a renaissance - its future has been guaranteed for at least another two generations.
That future has been built on a solid foundation of the accepted definition - not by re or de defining the music but by saying - "this is your heritage" take it as it is or go and do whatever you wish with it - the real thing will always be here if you want to revisit it".
That's why we now have thousands of young people playing and teaching traditional music - in some cases, to virtuoso standard.
Wouldn't have got here if the few people who dedicated their lives to building that foundation had decided to please everybody - that way, they would have ended up pleasing fewer and fewer as us oldies died off.
Jim Carroll