I dont understand why I would build on bluesky when it seems like it would have the same medium term issues that the twitter api had anyway, but enjoy it while it lasts I guess.
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Independent relays can exist, which is better than the fully centralized options.
There is no financial incentive to bear the cost of running a public relay.
In Activity Pub each node is essentially the full stack of what ATProto breaks up into individual entities. This means that each node in the fediverse is incented to connect to other nodes in the network, to provide good coverage to their users.