Wow, lamarca--good post. Personally, I think being too clear and concise is what creates so many stumbling blocks. At least, it seems to in the U.S. where traditional/folk/whatever term you wish has so many different origins and forms. But I guess the ambiguity of it bothers me less than it does some others. Besides, it's going to keep changing--what is not traditional now may have become ingrained in another 100 years (as the accordion has, even though it's a fairly new instrument), and songs that are currently not folk may survive in some form apart from their originals, as so many of the 17th century broadsides have.

I've heard a Western swing version of Richard Fariña's "Pack Up Your Sorrows" and a swamp Cajun version of Alan Jackson's "Achy-Breaky Heart", both of which are clearly not traditional and at least one of which is arguably not folk, but who knows? "Achy-Breaky" might die out as a pop country song but stay on as Cajun. (I doubt it, but then I would never have thought that "Chicken Reel" would stay so popular, either. I hate that tune.)