 Mack the Knife, it's one of the great American pop songs. When Berthold Brecht wrote it in Berlin in 1928, just before the rise of Hitler, he considered Mack the embodiment of the perfect capitalist, perfectly ruthless, vicious like a shark. But in 1950s America, Mack the Knife became a harmless, up-tempo, finger-snapping vocal hit. What happened to Mack the Knife?