OK, let's get the late comers caught up on the verified clues. This will help you separate the BS from what trusted people are saying is the truth.
Here's Carly's official website on the song:
http://www.carlysimon.com/You're_So_Vain.html
The David Geffen rumor was started by a London tabloid. Earlier when asked about the song she said her new album (2009) contained a clue to the identity of the person. They thought they heard David and jumped to the conclusion that it was David Geffen. Aside from Carly never having met Geffen before she wrote the song, he's openly gay.
Her publicist said it sounded like Daaaavid. This led people to believe that the guys name was David. Carly cleared this up by saying the word was "Ovid" and that she said it forward and backward so it came out sounding differently. She also said there is no V in the guys name and he's not known as David.
Carly has said it's a song combing the characteristics of three people. However, she's said "He" when referring to the song. So I think there is one main target and two lesser players.
She has said the song is a little about Warren Beatty. I'm assuming he's one of the three, but not the main guy. Warren
IS vain enough to think the song is about him because he called Carly after it's release and thanked her for it.
She told Howard Stern the three names. He said he remembers one being Beatty, one other may have been Geffen (But we know he's been ruled out.) and he said he can't remember the name of the third one which in my opinion is bull cookies. Stern also said one time that the interesting part is that the guy isn't that vain. So I believe the "forgetting" is so he doesn't get hounded about it.
There is an A, E, and an R in the person's name. (I'm very sure I heard her say one time that there was a B also, but nothing on the net backs me up on that.)
She's definitely ruled out James Taylor, David Geffen and Mick Jagger.
The guy is most likely still alive. Stern said "He isn't that vain." If he said "He wasn't that vain" then it would mean the guy is dead.
Start at post #66 and you'll see how I build my case for it being Bob Dylan.