The last time I attended a Newport Folk Festival, Janis Joplin was a featured act. She may still have been working with her original San Francisco bandmates, Big Brother and the Holding Company, or maybe not. (When Janis "hit the big time" with a major-label contract, the suits fired her hippie/acidhead band, assigned her an all-star session-player combo, and named it the "Full Tilt Boogie Band.")

Whatever year that was (1968 or '69, probably), there were still plenty of "real" folk acts on the bill, and even among the more modern electrified bands, most were arguably within an American folk traditon ~ such as Junior Wells & Buddy Guy and other urban-blues acts.

Times have changed; very few big-time big-money festivals are going to be presented without at least a few top-selling acts who are not going to meet anyone's definition of "folk."

For my tastes, and my own peculiar/personal idea of what consititutes "folk," there's more logic to including blues-rock, roots-rock, or even "classic-rock" ensembles ~ who at least present music that people can sing along to, or at least dance to ~ as opposed to some of the current singer-songwriter acts often classified as "folk," specifically those who do not invite audience prticiaption at all, but rather seem to expect a quasi-reverential brand of silent listening.