@Rick: seems like a possible error in this phrase, mentions both low energy cost and high energy cost at the same time:
"silicon photonic interconnects can sustain very high loads (over 100 Tb/s) with low energy costs (< 1 pJ/bit)...[but may] come at a relatively high energy cost."
@kris: IIRC, Facebook started the Open Compute Project, and Google decided to roll their own version with the Google Platform, so it doesn't surprise me these two giants go similar-but-unique with networking approaches, too. Also, some of the big Chinese datacenter outfits are coming up with their own versions. Part of that is probably not-invented-here thinking, but all these big orgs have many experts that define and redefine their applications' needs continually. I've seen some things indicating they are developing similar-but-unique architectures for storage, from RAM to flash to spinning/streaming media.
From a vendor standpoint that boils down to "give them what they want". But the larger and potentially larger (more lucrative?) market will be in adapting the high-end items developed for these customers to serve the midrange customers--who can't usually afford a cadre of system architects.
SDN seems to be rulling the datacenters..looking forward to hear about differences between Google and FB...I would think they would be aligned not clash, all they care from a hardware perspetive is cost...Kris