But Swift, 22, has always defended her right to sing about her exes. In Us Weekly's 2010 special collector's issue, Taylor Swift: Inside My World, the singer told Us, "I've always lived by the theory that if a guy doesn't want me to write a bad song about him, he won't do bad things. And he shouldn't, you know?"
She added, "I just write from my perspective about how it ended up and what I felt about it."
And Mayer certainly isn't the only ex that Swift has sung about.
She wrote "Forever and Always" about Joe Jonas, who famously dumped her during a 25-second phone call in late 2008. "It's alright, I'm cool," she later told Ellen DeGeneres. "You know what it's like, when I find that person that is right for me, he'll be wonderful. ... When I look at that person, I'm not even going to remember the boy who broke up with me over the phone in 25 seconds when I was 18. ... I looked at the call log —- it was like 27 seconds. That's got to be a record."
In 2010, she released the song "Back to December" on her Speak Now album -- which revamped her romance with the Twilight Saga's Taylor Lautner. "This is about a person who was incredible to me -- just perfect to me in a relationship -- and I was really careless with him," she said in a preview video for the song.
And a source tells Us that a song about Swift's most recent breakup with Jake Gyllenhaal will be included on her new album. The Source Code actor split with the country singer during the 2010 holiday season after an intense three months together.
"There's just been this earth-shattering, not recent, but absolute crash-and-burn heartbreak," she told Vogue magazine, "and that will turn out to be what the next album is about."
"["Dear John" is] cheap songwriting," Mayer told Rolling Stone. "It's abusing your talent to rub your hands together and go, 'Wait til he gets a load of this!' That's bulls--t."
He added angrily, "It was a really lousy thing to do."