Interesting thought that’s popped into my head since lemmy’s population blew up.

These services are essentially individual sellers that all come together on a centralised platform provided by these sites to perform these services.

Aside from the logistics and distribution I see little reason why they can’t be federated. Ebay could definitely be federated since individual sellers handle their own delivery, there is no ebay warehouse as far as I’m awar. Amazon on the other hand hold stock in warehouses making this considerably more difficult.