Guitar One, a generally wanker guitar rag, has a cover feature on acoustic guitar in the 10/02 issue (Tenacious D on the cover). The sidebar to the four-decade survey includes this, under "critically important unplugged tunes":
"Joni Mitchell 'Big Yellow Taxi' (1970) the queen mother of the female singer-songwriter domain was also a pioneer of alternate tunings in pop music." JT's "Fire and Rain" is also included in the short-list of 20. Denny, honestly not a GO subscriber--it just comes to my mailbox in a brown paper bag, delivered by a brown shoe'd square in the dead of night.