One of the most important fact form this article which is likely to be overlooked is : "the Prineville facility runs at 85°F with a 65 percent relative humidity". Running at such a high humidity + Temp combination is impressive esp when you look at the money saved in environmental costs.
Any idea on how much would it cost to produce a small quantity of those boards? At which scale does it starts to make sense to use a custom made motherboard instead of a off-the-shelf PC?
One thing to keep in mind is that one rack holds 90 servers and each battery rack feeds 180 servers, so (at least in Facebook's case) that's the basic unit. If this stuff takes off I would expect someone to produce a smaller 30-slot rack, though.