Well, think of it this way -- individual 1U servers can easily consume 1000W, or 1kW. Put about forty of those in a single rack, and that's 40kW. Divide 80MW for the datacenter by 40kW per rack and that's not very many racks to comprise the entire datacenter, right?
The footprint for 2000 racks would be over 1000m2; when you add the necessary spacing as well as supplementary utilities (power/networking) that probably means double that footprint.
I guess at the scale those companies are operating it's not that big, but that's still quite a large building !
