There's been some interesting articles about data centres lately. This one from ComputerWorld questions Microsoft's plan to use container based data centres (yep, as in you stick a bunch of servers in a 40 foot container). There's further follow up from Michael Manos here.
And don't miss the forest for the trees - they are talking about housing up to 440,000 servers on a single floor in a facility. Incredible. Facebook pales by comparison.