> > there is no rack space to compete for (there is competition for attention, that that is the same for every sellable thing).

> So, how much is the front page of Amazon worth or the featured section of the iBooks store, since that is the digital equivalent of the front of store in B&N?

That is what I was referring to as "competition for attention". You can only suggest or push a limited number of items but this is different from competing for rack space: you just cannot afford to have on your rack all the books you could sell. You must also choose how many copies of each book you should put on the shelves. All these aspects are no longer relevant when you are selling "bags of bits".