Developers need faster cores, not just more of them.
For the last several years Intel seems to have thrown in the towel on making individual cores significantly faster, instead simply relying on process shrinking to cram more of the same into a chip package. Unfortunately for the rest of us, most software on planet earth does not take much advantage of increasing numbers of cores, infact some stuff actually slows down marginally as more cores are added!
Taking multi-core out of the equation, looking at single cores only, Moores Law ran out of steam at Intel somewhere around 2004.
That said, how a platform like Facebook with its thousands (tens of thousands?) of concurrent users can fail to take at least some advantage of hyperthreading within a core and a shift from 2 to 4 to 6 cores is beyond me. Perhaps they need better developers? Consider a move to developing in Erlang?