The idea would be to use IP addresses for all levels of routing, and MAC addresses only on the endpoints to identify the connection. So routing actually becomes simpler. However, you have a good point about privacy. One of the other commenters also mentioned non-unique MACs.
Another point against using MACs which I want to point out is that they don't make much sense if you have a service running on multiple hosts. I mean, you could introduce "virtual MACs", but it seems better to keep the idea of "service ID" separate from "device ID". Session IDs solve the multiple hosts problem too, by completely avoiding it.
Another point against using MACs which I want to point out is that they don't make much sense if you have a service running on multiple hosts. I mean, you could introduce "virtual MACs", but it seems better to keep the idea of "service ID" separate from "device ID". Session IDs solve the multiple hosts problem too, by completely avoiding it.