I mean yes, but that’s not a federation problem.
To completely strawman AND slippery slope what you’re saying:
As a car safety pro, who primarily deals with car crashes:
STOP
TOWING
TRAILERS
Agreed, dangerous, I don’t want numpties doing it.
But it’s a large part of why I have a car.
I want to be clear, that I disagree with his “federation is stupid” point, but email has problems right now.
Theoretically it’s federated, theoretically you can spin up your own mail server and self host.
But even if you do that absolutely perfectly (SPF, DKIM, DMARC etc), you can falsely end up on spam list, that effectively block delivery of your email to large segments of the network for days if not weeks.
Whilst theoretically federated, email falls under the broad dominion of google, microsoft and a couple of other large players.
Individual instance owners can do literally whatever they like.
Put up ads.
Charge a subscription.
Anything.
Let’s say instance A is hosting a community that everyone on instances B and C love to participate in.
But A want’s to earn some money so they start charging access to their local users.
This doesn’t effect users of B and C at all, because the data is federated.
The owner of A get’s grumpy and defederates B and C.
The users on B and C find somewhere else, either on one of their instances, or on D.
Everybody wins.
The Back to the Future trilogy is good for a re-view.