When is it that my iPod earbud cord goes from "nicely wrapped around iPod" to "irritating tangled mess"?

It drives me crazy having to untangle them all the time and it made me wonder: when do they get tangled? Is it when I put the iPod in my pocket/bag? Is it when I pull it out? Do they just spend all the time while in my bag/pocket not being used to slowly twisting into a bunch of knots? Is therea magic Knot-in-Cord Fairy who devilishly goes around casting spells on the cords so that we all have to spend ten seconds untangling our cords with the music player tucked awkwardly under and arm or held between knees before we can listen to our music?