[Hat tip to Richard Bennett for the recommendation here..] I haven't had a chance to read through the entire thing yet, but this new study by Nemertes Research seems worthy of attention: "Internet Interrupted: Why Architectural Limitations Will Fracture the 'Net." From the exec sum:

In 2007, Nemertes Research conducted the first-ever study to independently model Internet and IP infrastructure (which we call "capacity") and current and projected traffic (which we call "demand") with the goal of evaluating how each changes over time. In that study, we concluded that if current trends were to continue, demand would outstrip capacity before 2012. Specifically, access bandwidth limitations will throttle back innovation, as users become increasingly frustrated with their ability to run sophisticated applications over primitive access infrastructure. This year, we revisit our original study, update the data and our model, and extend the study to look beyond physical bandwidth issues to assess the impact of potential logical constraints. Our conclusion? The situation is worse than originally thought!

We continue to project that capacity in the core, and connectivity and fiber layers will outpace all conceivable demand for the near future. However, demand will exceed access line capacity within the next two to four years. Even factoring in the potential impact of a global economic recession on both demand (users purchasing fewer Internet-attached devices and services) and capacity (providers slowing their investment in infrastructure) changes the impact by as little as a year (either delaying or accelerating, depending on which is assumed to have the greater effect).

This is a subject that my colleague Bret Swanson has written a great deal about, so I'm sure he'll be commenting on this study at some point. Even if you don't agree with the conclusion Nemertes reaches, as Richard Bennett notes, the report is well worth reading just the background information on public and private peering, content delivery networks, and overlay networks.