@feditips mmm, well... Twitter is on one domain but that doesn't necessitate one server/instance. There are some giant Internet systems and they can be distributed and redundant under the covers. It's certainly true that the owner of the domain has considerable power with regard to the services offered and control of who can play among them and how. That's the "centralization," seems to me. I don't want to think of the ways that the fediverse can be disrupted, including from within.