What a spin :"[T]he only salient characteristic shared by all owners of portable music players was that they were more likely to buy more music -- especially CDs.' This is despite years of iTunes promotion and apparent success."

The success is not apparent, it is real. They are making real money from real people. I would say: "Considering that only 20 tracks are from iTunes, then the potential for growth is huge because doubling everyone's purchases simply means convincing them to spend an extra 20$".