"And some flows through so-called dark networks, private channels created to move information more cheaply and efficiently within a business or any kind of organization. For instance, Google has privately built such a network so that video and search data need not pass through so many points to get to customers."

Can someone please clarify exactly what this means? What exactly do companies like Google do to move the data more efficiently within their own network?

I don't have any info about what Google is doing, but they could be doing "cold potato" routing by sending traffic over the GoogleBone all the way to local ISPs, bypassing the other backbones.