The nice thing is that there is a setting to specify where the location is if you prefer a certain implementation or host. Which I think is another example of how well designed npm is. My question is, is there a way to evolve the protocol a bit to be more practical for ensuring that multiple "central" registries are able to stay in sync? Or is the current system which is tied to Couchdb replication specifics (I think) the best way?

I agree with the general idea of separating out the concern of the metadata index from the actual hosting of the packages. I also agree that its important though to keep changes transparent and practical for people to implement on their own.

I can't help but mention one more time how interesting these issues are in relation to what I see as an inevitable move from a fundamentally server oriented network architecture for the internet to a fundamentally distributed data oriented architecture. And that change presents many challenges including how it intersects with business interests.