I'm not among those who believe that anything not sung by a horse is a folk song. Elvis in Vegas is not folk. I think that now, with the dominance of mass media it is impossible for a legitimate folk tradition to thrive (as opposed to people like us singing folk songs from the past.) However, as late as the fifties there were grassroots regional styles developing in America, like rockabilly and Chicago blues which would fit any objective definition of folk music. The fact that they later became extremely popular is irrelevant. Two hundred years ago it would have been absurd to say a song was too popular to be folk. If rockabilly had not become popular it would have the same status today as other regional folk styles like Cajun and TexMex.

I do realize that there is no one definition of folk music. In a sense, we all know what we're talking about when we say "folk", it just breaks down at the edges. Mudcat would not be the first place I would look for information on rockabilly. It's hard to imagine, though, a definition of folk that would include, say, the Carter Family but exclude Carl Perkins.