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In this example instances are stores, stores are users in instances? How stores are protected to be defederated by competitors (we are talking about money and making a living here).
What it adds to just a simple centralized service that any store can join. If you don’t want it to be another amazon, make that service a coop. or some kinds of non-profit that it’s paid by the stores that want to become part of that.
I think here we are in the classic conundrum of “a solution in search of a problem”.
Fediverse and ActivityPub is cool, but it’s a social media thing. And decentralization is cool when needed, for instance social media. But it doesn’t have to make sense for every use case.
For what’s being proposed there’s zero actual need for decentralization or ActivityPub.
Those admins are unpaid?
Managing a store it’s a LOT of work. And you are doing to provide profit for other people. Who is going to do it for free?
It’s not like social media where people may volunteer to admin and mod, and users may donate because it’s a common goal of share information, opinions, knowledge, funny stuff etc.
Here we are talking about bussiness that do what they do because they want money. I would not volunteer to admin a store so shop owners could earn money, that’s for sure.
And I still not see the advantage of doing within the ActivityPub instead of just being a normal service where all interested shops could join.