The telling lyrics: "Dear John, I see it all now that you're gone / Don't you think I was too young / To be messed with?"
Who it's supposed to be about: John Mayer
Why? Well, it's called "Dear John," after all! After Swift and Mayer collaborated musically, the song came out, and Mayer opened up about how it made him feel: "I never did anything to deserve that. It was a really lousy thing for her to do."