I hope Nintendo doesn't pull "an AOL." AOL tends to use nonstandard garbage. For example, you have to buy an "AOL compatible" router to share an AOL Broadband connection, and such a connection isn't “always on” or compatible with any console gaming network.
How does this relate to Nintendo? I think Nintendo should embrace the technology that already exists. For example, I'm living in a duplex with one of my sisters. Downstairs, another of my sisters lives. She and her kids have a GCN, and so do I. We already have a three computer network, one of them downstairs. It would be nice to be able to unplug two of the Ethernet cables from the computers and plug them into the GCNs, forming an instant connection. This is how standard Ethernet stuff works. The router (with switch), switch, or hub handles the traffic direction (I think).
If I understand it correctly, if Nintendo follows the Ethernet technology already in existence routers (with switches), switches, and hubs or any other Ethernet stuff I don’t know about should work. The computers (be they Macs, PCs, Xboxs, or GCNs) don't care about what happens in the middle as long as the communication happens. As far as the Internet thing goes, even broadband is significantly slower than 10mbps Ethernet and if Nintendo uses FastEthernet (pretty much the standard now at 100mbps), broadband is about 100 to 50 times slower. I guess it all depends how much bandwidth the game needs. Even with online tricks, you'd still only be able to connect two GCNs though.