This is the digital corollary of the law that states that all tapes left in a car for over a fortnight turn into "Best of Queen" albums.
Buying music on the internet is much too easy, and much too inexpensive. When once you might have hesitated over shelling out twelve bucks for the new Tal Bachman CD, it's pretty easy to justify 99 cents for a track of Jimmy Buffett.
Which is why, ten years later, your music is on shuffle while you're throwing a party, and your squirrelly Judas of a computer plays "Margaritaville." You can't remember buying it. You can't remember ever being in the state of mind that would prompt you to buy it. But there it is.
That, and an astonishingly large pile of Manchester United songs.