iTunes and friends have nearly killed off the radio. But is iTunes itself next to go? Trends in technology change so rapidly that what was gospel yesterday can be apocryphal tomorrow. To wit, the music business, which looks poised to undergo another upheaval — and put an end to per song sales from the likes of iTunes and Amazon. It was just over a decade ago that Apple introduced iTunes — called both the Grim Reaper of the music business or the fairy godmother that saved songs from the clutches of illegal file sharing sites such as what was at the time Napster. Many decried the tinny digital music files and the loss of high fidelity CDs, but the writing was on the wall: Convenience trumped clarity.