Today Facebook announced the Open Compute project which has allowed them to build more efficient data centers by tackling the hardware scalability concerns.
A team of Facebook engineers spent the past two year focusing on scaling computing infrastructure to find efficient and economical ways to grow. Working out a lab the team designed a data center from the ground up; a few months later they started building it in Prineville, Oregon. The project started out with three people and grew to building their own custom servers, power supplies, racks, and battery backup systems. Essentially they designed and built everything from the ground up to be efficient and very cost effective.