Covering other people's material is a mainstay in pop music. Why bother taking the time to write an original song when you can just recycle somebody else's hit, redo it with an acoustic guitar (or, if it's an acoustic song, with an electric guitar) and generate the same result? But it doesn't always work out as planned, especially if you don't bother to figure out what made the original song popular in the first place (or in the case of our #1 choice, even bother to learn the damn lyrics first). Below, 20 great songs that received sound butcherings by artists who should've known better. A lot better.