Snip from a worthy read about shifting network meta-architecture, by John Markoff in today's New York Times:
[Peering] goes back to the earliest days of the Internet, when organizations would directly connect their networks instead of paying yet another company to route data traffic. Originally, the companies that owned the backbone of the Internet shared traffic. In recent years, however, the practice has increased to the point where some researchers who study the way global networks are put together believe that peering is changing the fundamental shape of the Internet, with serious consequences for its stability and security. Others see the vast increase in traffic staying within a structure that has remained essentially the same.
What is clear is that today a significant portion of Internet traffic does not flow through the backbone networks of giant Internet companies like AT&T and Level 3. Instead, it has begun to cascade in torrents of data on the edges of the network, as if a river in flood were carving new channels.
Scientists Strive to Map the Shape-Shifting Net (New York Times)