When: November 2009-January 2010

They say hindsight is 20/20, right? Well in retrospect, perhaps old Johnny boy should have left this one alone. Though the pairing initially seemed to be a match made in attractive musician heaven, it didn't end so well. After the couple's tumultuous break up in 2010, Taylor let her feelings on the situation be known in the only way she knows how: She sung about it. She released a song, the aptly titled "Dear John," in which she detailed Mayer's "dark twisted games". 

Smash Probability: Taylor didn't book studio time to vent about the dude for nothing.