From what I understand, very few or nobody actually knows who the song is about other than Carly. The idea is that if that person hears her song, even though it never directly mentions them by name, will still think the song is about them, because of how vain they are.

Edit: phrasing.

I want someone to power scale the Old Man, dude had enough strength to do what 4 bricks at nearly terminal velocity, a couple dozen paint cans, a swinging metal pipe, an entire tool dresser, and a fuckin' blowtorch with one shovel swing.