The Million Server Data Center

What would it take for a data center to house 1 million servers? The IEEE Spectrum magazine tackled that question recently as part of a feature on mega-data centers prompted by the enormous server farms being built by Microsoft, Google and others (link via James Hamilton). The magazine offers its own vision of what a million-server data center might look like - a huge facility filled with 400 shipping containers, each packed with more than 2,400 servers and cooled by a central cooling system that pumps coolant into the rear of each bank of racks.

Is such a facility ever likely to be built? Is the hypothetical facility outlined by the IEEE the best approach to this kind of scale?