There has been some recent chatter on the internet about the possibility of Apple introducing a subscription based service. Steve Jobs may have just put that speculation to rest:
"Never say never, but customers don't seem to be interested in it," Jobs told Reuters in an interview after Apple reported blow-out quarterly results. "The subscription model has failed so far."
This was reported on CNN.

What's interesting though is the language Jobs uses. He says customers don't want to rent their music. However with iTMS that is exactly what you are doing. Ok, maybe it is more of a lease, but customers certainly don't own it. The ULA makes that pretty clear. And as long as there is DRM, you are more of a renter than an owner with music purchased from iTMS.