The Internet's early architects built the system on the principle of trust. Researchers largely knew one another, so they kept the shared network open and flexible -- qualities that proved key to its rapid growth.
But spammers and hackers arrived as the network expanded and could roam freely because the Internet doesn't have built-in mechanisms for knowing with certainty who sent what.
The network's designers also assumed that computers are in fixed locations and always connected. That's no longer the case with the proliferation of laptops, personal digital assistants and other mobile devices, all hopping from one wireless access point to another, losing their signals here and there.
One of the great advantages of the current infrastructure is openness. Information flows are almost frictionless and the potential for collaboration is tremendous. That may benefit some kinds of information and knowledge exchanges, but not all. That same openness may discourage important inputs and kill potentially beneficial interactions.
I liken the tension between the old and new information infrastructures to that of open and closed virtual communities. Open communities are experiments in anarchy. This is a great approach if your goal is as many contributors as possible. However, the quality of information exchange is poor and knowledge production is sorely lacking. Closing the community to a smaller group of people benefits collaboration, but limits the breadth of ideas and experiences.
Greater accountability and trust are needed. Ideally, you could have an open community with high quality interactions. Clean slate projects could produce such a society, but would the number of users go down? I think many of the problems could be solved via social innovation, but I recognize the need for a secure network among members of a closed community. That's fine, as long as we don't lose the "old" internet.
When I imagine Network Pittsburgh, I see a relatively open community with creative approaches to problems of trust and accountability. However, given the research going on at CMU, perhaps Network Pittsburgh would be a great pilot for a clean slate project.