Matt - I don't think any folksingers called themselves "folksingers" until musicologists did. I think a distinction can be made, though a flimsy one, as good as any other flimsy definition of folk - to make folk music in the living room (like Daniel Johnston did in the late 70's and early 80's) and to do it yourself with the most limited supply of resources is quite exceptional.

You seem to be treating folk as a genre, which it is not, no more than classical and popular can be considered genres. It is better to consider them as categories of genres. The genres that make up folk are blues, railroad songs, depression era songs, irish republican songs, and much, much more. Then, if folk is a collection of genres, how can it be a genre in itself. This applies to classical music also. Classical music is a collection of classic genres (waltz, march, minuet, aria, sinfonia, bagatelle, bouree) and hundreds more. Then how can classical be a genre, itself being consisted of genres? Apply the same to the word popular. Actually, when you look at it this way, much of the source of confusion begins to become apparent.