On page 10 of the new corporate presentation it references a Microsoft example of spines/leafs. Here are sone articles about what those nodes are and how designs are made to connect all those servers and switches. Thats a lot of increasingly optical cabling.
http://www.cisco.com/c/dam/en/us/td/docs/solutions/Enterprise/Data_Center/MSDC/1-0/MSDC_AAG_1.pdf
http://bradhedlund.com/2012/01/25/construct-a-leaf-spine-design-with-40g-or-10g-an-observation-in-scaling-the-fabric/
rogue