Check out Ruinedmusic.com, where readers submit songs that are ruined for them for one reason or another (but usually by a bad break-up).
For me it's "What it Takes" by Aerosmith. I listened to that song after "breaking up" with my middle school "boyfriend." Picture me, feeling all maudlin, thinking, "Oh Jason, tell me how it is that you can sleep in the night without thinking you've lost everything that was good in your life to the toss of the dice?" Gag.
Another is "Vivrant Thing" by Q-Tip because that was on the radio one time while my last ex was getting gas and he was dancing around to it at the pump. If I knew then what I know now I would have shoved him to the ground, run over him a couple times, and driven away. Hindsight is 20/20.
Do any of you have ruined songs?