Joni Mitchell sure isn't plagiarizing. Those fucked up tunings and chords she uses are so unique they're completely inaccessible - to my ears anyways. I shouldn't sound like I'm disrespecting her, I just can't get into her at all ... And, yeah, in cahoots with everyone above, folk music is all about plagarizing. Steal a lyric, steal a melody, steal a whole song and write two new verses ...