Well, that sort of comes back to the old adage, "If more people peered in more places where they just happened to be collocated in the same place, the internet would be a better place." For example? All the amtrak collos on the northeast corridor...
Infact a lot of "backbone to backbone" peering is still done with DS3s (think of the content providers with little need to talk amongst eachother in bulk, GlobalCenter, Exodus, AboveNet, etc). The interesting traffic is where the data providers (like those mentioned above) meet the data suckers (@Home, AOL, etc), especially as streaming media takes off.
If we had a few more PAIX's and Equinix's in strategic locations the internet would be a better place. :P
-- Richard A Steenbergen <ras@e-gerbil.net> http://www.e-gerbil.net/humble PGP Key ID: 0x138EA177 (67 29 D7 BC E8 18 3E DA B2 46 B3 D8 14 36 FE B6)