Maybe we can derail the "What is folk" discussion by reframing the question. Rather than asking if Steve Earle is "folk", what would you call his dominant style of music. I know he has written some songs, particularly lately, that are specifically "bluegrass". But the type of song that he wrote with the Dukes and that writers like Towns Van Zant, Guy Clark, Billy Joe Shaver, Kevin Welch and a bunch of those old Texas boys (and girls, lest we forget Gillian Welsh, Lucinda Williams, and others) are producing are sans genre. They aren't strictly country, whether you attach "and Western" or "alt-" to it. It has a lot of country in it (small "c", thank you very much) and is highly blues influenced. I kind of like "roots" music, but that ties it to cajun, zydeco, reggae and a bunch of other stuff that it ain't.

There is a radio show from the College of DuPage in the Northwest Chicago suburbs called "American Back Roads" that plays all of this kind of music. Hearing Otis Redding or Rufus Thomas back to back with early Elvis, or Hank Williams and then hearing how modern writers incorporate and build on all of those traditions makes the connections quite clear. Another place to hear the connections between styles and forms is on the Chieftain's "Long Black Veil" album (they did another one in that vein, but the title escapes me). That's the "musical real estate" that I find most interesting these days. You can keep the top 40 - I'll take the back 40 everytime.