Probably a dumb question, but don't federated services eventually lead to centralization? for example SMTP is federated but most users are on gmail, IRC is decentralized but most users are on freenode server, etc. users tend to choose the services/instances with the most users, which is what makes github currently very valuable.
Gmail killfiled a domain I was running on a small but reputable ISP I had used since 2001 (there were no spam or reputation issues in 17 years).
They did let one-in-20 or so emails through, but everything else got to gmail recipients’ Spam folder. I wasn’t able to troubleshoot this with Google tools, and there’s no one to talk to at google.
(Worst thing, you get no feedback - except realizing a month later that someone didn’t get an email you sent)
I gave up and replaced small ISP with fastmail.
My bottom line is that, no you can’t really run your own SMTP server anymore unless google, Microsoft and fastmail let you, by virtue of hoisting 90% of your recipients.
Sure, something like that can happen... but it is not like they have an explicit "allow-list" of domains that mail can be received from. These might be the biggest providers but if me and my friend who do not use their services want to communicate, we will always be able to do so without them.
I have many domains that I use to send and receive mails, and I have personally never had these issues.
Now if I did have a gmail account, I suppose I would have to check the spam folder regularly. But I don't have that problem with my server, it affects their users more so than me.
in the current world, you host your code on github and you can only submit prs to github with a github account. anyone without a github account cannot submit a pr. github hosts all the code.
in a federated world, while github may still host all the code, you could potentially submit prs with and have metadata about a repository, such as issues, spread across multiple different providers. Instead of needing a github account to contribute, you just need an account that github could federate with.
This would mean that if Github did start doing something you didn't like, you would be able to change code host without losing the metadata.
Potentially, anyway.
Federation doesn't prevent centralisation if the service is good enough; it just makes it less painful to decentralise if better competition exists. It also diversifies ownership of data, which is in general a good thing for consumers - and a bad thing for big tech companies that wish to make money off of analytics, which is why we will never see current social media platforms allow federation with other social networks, even if would be better for the world and consumers.
IRC isn't federated in that sense, users on EFnet can't interact with users on freenode, so the network effect works in that case.
Gmail has an enormous market share (about 40%) but I don't think that's related to the nature of SMTP, more about their incredibly competitive free tier and the decidedly not federated groupware for their business offering.
