Day 2 of IPAM also had a bunch of interesting talks. My favorite for the day was by Ramesh Johari, who was considering the following problem: suppose that you only allow bilateral transactions -- corresponding essentially to a barter system, or in his view roughly how BitTorrent currently works. (People upload to you if you download to them -- not necessarily the same amount, but there nominally should be some equivalence in terms of utility.) How much do you lose over a system where you allow multilateral transactions -- which corresponds to the system we all know and love, where there's money behind exchanges, so you can always get money and use it to buy something else later. He set up an interesting model to look at these questions and say something meaningful about the differences between the equilibrium states in these two settings.
David Alderson also gave a very interesting talk on modeling the Internet topology using optimization methods, and using it to study the scale of the damage an adversary could do to the Internet. His point of view is very different (and I think much more compelling in the Internet setting) than the scale-free analysis popularized by for example Barabasi. I recommend checking out his papers (most of them co-authored with Doyle and Willinger, among others) on the theme.
Finally, I ended the day nicely by getting to talk with UCLA faculty Rafail Ostrovsky and Amit Sahai. Rafail expressed his usual enthusiasm insisting that we find a problem to all start working on -- so now I even have homework to keep me busy on the plane ride home!