My understanding is federated "payment" systems are difficult. I think there is active discussion on the topic, but I'm not sure where code/development is at, or if it's even started.

I think flohmarkt ("federated decentral classified ad software") is the closest we have right now. It has low (~10-30) Monthly Active Users (MAU), but is in active development.

Services like eBay are part platform, part people. eBay's people do a lot behind the scenes to ensure it runs smoothly and ethically... AND they take a significant chunk of the proceeds. You could put up some free software that does auctions but you wouldn't have all those high paid security and trust workers working for you.

We could start a buy/sell/swap space using existing Lemmy technology, if we left the messy details for users to figure out for themselves.

Messy details add up quick, though. Payments, currencies, mailing addresses, reputation, conflict resolution, returns, scammers and spam.

But "Craigs List" solved very little of that on day one, and went on to be pretty successful.

So it's ~~possible.~~ happening now, I've just learned. Neat!. https://lemmy.sdf.org/c/buyselltrade

(Edit: Added link to the surreal thing. Thanks!) (Edit 2: I swallowed the onion whole. Mostly jokes, there, I think. I'm gonna leave the link anyway.)

...flohmarket?

You mean as in an auctioning platform? That's legally a bit harder to achieve, as auctions usually have the rule that if nobody outbids you, then your offer is binding. To enforce that, instances would need to verify your identity. That's easy for a larger company to do, but not that easy for hobbyists.

And then, to be federated, you would also need to make sure that other instances that you federate with uphold that standard.

Also, if you do auctions across international borders, how do you even prosecute somebody who does not obey the rules of an auction?

I mean theoretically, sure. Realistically, no. Because people would reneg on their offers, and you have no recourse as a seller.

I have seen the fhlomarkets in the past, I’d love for them to take off but uptake is slow and usually it’s odd items at ridiculous prices.

I know there was a post on lemmy/piefed from a Melbourne based guy who added a site he was working on a few months ago. Not sure how it went but he was open to talking about how he set up and what he was hoping from it.

A federated ebay is basically impossible. For that you would need real time communication between different instances. Otherwise people on the sellers instance would have an advantage in winning the auctions, defeating the purpose of making it federated in the first place.