How does defederation work? Is it global or is it in a per instance basis?

Yeah on the whole it could be good, In the same way that it isn't a problem that google owns the most popular e-mail service, that doesn't hurt those on proton mail or any other mail service, and in fact offers benefits that they can just as easilly e-mail their friends using gmail from their preffered mail service. The real fear is the embrace extend extinguish. IE if meta encourages people to join their instance, then gradually makes things incompatible after major communities move to them, but they can't prevent us from moving back just the same even if they somehow got us to jump there.

This "anyone is free to join any instance, you can just avoid what you don't like" kind of thinking is perfectly reasonable in theory, but I think what OP wants to know is if this also holds up in practice. You could "defederate" Google and Microsoft by blocking emails from Gmail and Outlook addresses, but the reality is that the majority of people you will need to contact use those addresses. In most cases, your school/workplace will even make you use them for your organizational email. Yes, it is possible to avoid these companies and choose alternatives, but you'll be isolating yourself from the majority of the network.

The question is not if it will be possible to use the future corporate-owned Fediverse without Meta (of course it will), but if it will be feasible for the majority of users.

let's say the instance i belong too has been bought out by zuckerberg... can i transfer my data and move? or do i just lose everything like i did with reddit?

A good analogy is Google with Gmail. They became the biggest player in email and even gained a lot of influence over for email works, but you can easily use another email provider and not be locked out of the system.

Imagine how horrible things would be if email were centralized. We really need to thank the founders of the internet for having the foresight to not let that happen.

Or, they just won’t care

Seems simple enough to me.

Meta: Do what we want or we'll defederate you!

Everyone: Fuck off

Meta: Surprised pikachu

Great article! I appreciate how it addresses the commonly raised reasons and points to a way forward.

Good read. Onboarding and discoverability are the weakest part of the fediverse and need to be a high priority.

Apps should go as far as assigning new users randomly to a good general instance (vlemmy.net, lemmy.one, lemm.ee etc) if it means the user wouldn't have to know about instances, and integrating lemmyverse.net's functionality into lemmy would both go a long way for both I feel.

They're supposedly in talks with activitypub, the backend of the entire fediverse. If meta can get what they want with activitypub, they'll effectively have control over the entire fediverse. I don't see that happening though because the fediverse was made in opposition of major social media sites. I see them trying to take control of the software like lemmy and kbin or if that fails trying to buy popular instances or just filling the fediverse with their existing users. Luckily if the first two fail the nature of the fediverse works in our favor and the instances that want to can just defederate.

If they start taking control of a large, established base

We are not a large base. Lemmy+kbin have only a couple millions of users, and Mastodon 13 millions. Facebook is planing to migrate all Instagram accounts to P92 accounts. That means billions of users, flooding the whole fediverse.