@cwebber Yeah, I think you are completely right about comparing it with search engines. At least, this seems to be the expectation of BlueSky itself.
From BlueSky's blog:
"The federation architecture allows anyone to host a Relay, though it’s a fairly resource-demanding service. In all likelihood, there may be a few large full-network providers, and then a long tail of partial-network providers. Small bespoke Relays could also service tightly or well-defined slices of the network, like a specific new application or a small community."
https://bsky.social/about/blog/5-5-2023-federation-architecture