Sam Smith stole a Tom Petty song, which is a grand tradition in pop music

Sam Smith, a secret Tom Petty fan? Or perhaps a subconscious one? Apparently, the mopey soul man's biggest hit, "Stay With Me," was so deeply influenced by Petty's 1989 smash, "I Won't Back Down," that the British star and his co-writers are going to share songwriting credits with Petty and his co-writer, Jeff Lynne. (Listen to a fairly damning mashup of the two songs in the above video.) Believe it or not, in the pop world there's a rich tradition of ripping-off other musicians -- and having to...