As Sheila Weller writes in Girls Like Us , the song had been written in four parts. Carly sketched out a melody with the chorus "Bless You Ben". Then on an airplane her musician seatmate pointed to his cup and said "Doesn't that look like clouds in my coffee?" Then, thinking back on some of the men in her life she wrote her most famous lyric "You're so vain; I betcha think this song is about you". It all came together when a man she knew walked into a party ( "like he was walking onto a yacht").
Weller suggests the way Warren Beatty and Jack Nicholson shared girls led to the line "You gave away the things you loved; And one of them was me".
When Carly sat down to play "Ballad of a Vain Man" on that May day, Perry grabbed his bongos and started pounding out a thunderous beat. The first time he heard the song Perry says he knew it would be a hit.
Released on December 2, 1972, with backing vocals from Mick Jagger, "You're So Vain" topped the charts for three weeks in January.
Frankly, I've read so much about who might be the subject of the song, I've stopped caring.