> I don't know a whole lot about XMPP, but since it's federated, wouldn't it have the same avalanche?

It absolutely did. Everyone decrying how XMPP federation was killed conveniently forgets how useful it was to spammers.

Since this is IM the most you could do would be to generate a lot of requests to put the spammer on someone's roster list. In the unlikely event that a particular rogue XMPP managed to convince anyone to let them add some bogus users to their roster before it was blacklisted, it would take literally seconds to resolve the issue by removing them from your roster. So there isn't really any incentive to do spam over something like XMPP.

I have been on the federated XMPP network pretty much as long as it has existed and I have not gotten a single spam attempt. I guess I could post my jabber ID somewhere to make it more sporting (they need that to even try) but I really don't want to add random people to my roster. Email is intrinsically different that way.