Well I didn’t disagree with your suggestion that the song was inspired by multiple people (I said so in our little back-and-forth). I was disagreeing with the notion that there are supposed to be multiple characters in the song. In other words I believe she’s singing to one character, a fictional character who is a composite of real people she knows. I may have misinterpreted your post in that regard, I’m not sure. But congratulations on being right about the multiple inspirations. 
Wait, are you saying that Carly Simon wrote “You’re So Vain” about Yogi Berra?
Yogism: I’m very proud of being so humble.
I think that was a common conclusion long ago.
I think we know who the song is really about!
I just read a review of her memoir Boys in the Trees in the NYTimes. The reviewer, Janet Maslin, basically says that Simon tries to dispel the notion that she was a child of privilege, and was really a victim of parental dysfunction which extended to her relationships. The bookflap refers to her as a “feminist icon” and yet her whole book is structured around men and her relationships with them.
Seems maybe she’s the vain one.
Her childhood, not to mention her marriage to Taylor and her many other romantic relationships, is detailed at disturbing length in Girls Like Us, mentioned above, and nothing in the Maslin review added anything to that.
If people haven’t read Girls Like Us, it’s worth getting. Really three mini-biographies, but mini is often better than maxi biographies.