How much square footage does one really need to support iTunes in the cloud? I suppose their market share puts some pretty heavy demands on scalability, but a

How much square footage does one really need to support iTunes in the cloud? I suppose their market share puts some pretty heavy demands on scalability, but a 500k sf datacenter is a lot of datacenter, and storage is fairly dense these days. Add to that the fact that music files deduplicate very well across millions of people and I'm left wondering if they're doing photos and video too, or something else altogether, or if my back of the envelope estimates of the square footage requirements for such a service are just way off.