Lyric discussion by Hyperbole 

Cover art for Lull lyrics by Andrew Bird

I think the last stanza's rather funny, as it's a play on Carly Simon's "You're so Vain," which could have been about Mick Jagger, Cat Stevens, Warren Beatty or Kris Kristofferson.

NIN later put the lines, "You're so vain, you probably think this song is about you You're so vain, I'll bet you think this song is about you Don't you? Don't you?" into Starfuckers, Inc.

See the word play? He wrote a song about himself. It's definitely about jerkin it.