I feel a major rathole opening up, but when has that stopped me... This seems logical, this seems to make sense. And then we have the hub-and-spoke model brought about by airline deregulation and FEDEX. There you have an entire industries built out of moving people and goods from end points to central sorting facilities and then back out to their destinations. Think of O'Hare as a the MAE-East of the FAA.AIRNET. Yes, I know there are no 'pure' examples. Even FEDEX tries to intercept local packages before they get on the planes, and route them via local trucks. Like most things, there isn't a 'pure' answer. It is efficient to have a few (we can argue over the number, 3 NAPs seems to small for today's Internet) hubs. But it is also efficient to try to intercept local traffic, and handle it locally (local exchange, caching, etc). Of course, living in the St. Louis TWA hub city, you may understand why I don't always think letting a single carrier domainant a hub is a great idea.
In large metro areas, or any place with a large *number* of ISPs, there will be advantages to local interconnects. Period. Even if there is distance-insensitive pricing for their connection to a MAE-thing, I would think that they would rather save that precious bandwidth for traffic that really needs to go to the MAE-thing. It could reduce their need to buy a bigger pipe to that major interconnect, just to carry that local traffic "up-and-back". -- Sean Donelan, Data Research Associates, Inc, St. Louis, MO Affiliation given for identification not representation