> if Threads becomes too successful for the Fediverse.

I wager most Fediverse users aren't worried about this (at least speaking for myself). The status quo is 2 or 3 big private companies and a few thousand federated alternatives. If Meta betrays the community, things will go back to square one and core functionality of their app will start to falter. They need the community more than the community needs them.

When threads goes live there will be tens of millions of people with existing Meta user profiles entering it overnight. There are currently ~13M Mastodon users, most of which I'm sure are not really active. So depending on how federation into ActivtyPub is set up, it will be like Eternal September x 100. Their content will likely dwarf anything out in Mastodon land. And judging by what I see on Facebook and Instagram, I don't hold out high hopes for the quality of that content or the behaviour of those users.

I'm not worried about it really because I think the ethic of fediverse as such that they will be quickly de-federated. But it won't be fun along the way.

Mastodon doesn't fill your timeline with content from other instances, by default. If 100 million Facebook users federated with Mastodon overnight, 0 organic Meta-related posts would make it into my timeline. Only content reposted from Meta by people I follow would show up.

Defederated or not, Meta will have pretty much zero bearing on the instances outside their bubble.

This is true, though people from Threads will likely be able to follow, and comment on Mastodon profiles and posts and cause issues that way.

"They need the community more than the community needs them."

You have to be kidding me. The entire fediverse is little over 1M MAU, almost all of them not monetizable. So...tiny and useless. Threads can launch whilst being fully defederated and instantly become the fediverse.

All of this is true, but none of it contradicts what I said. Meta needs Federation to flaunt the bigwig researchers and developers from other instances. They will eventually build their own stockpile over time, but they wouldn't start with ActivityPub support if their intention was to eventually remove it. If Meta leaves the Fediverse, it goes back to how it is today. That's not a nightmare scenario for most people who are already using Mastodon, and it would put the leverage back into the hands of the users who could coerce Meta users to switch instances for more lax federation.

The ActivityPub ecosystem stands to lose nothing either way. Meta is walking a fine line with the remainder of the community that trusts them, but stands to integrate into a pretty nice system if they pull things off.

Alternative trajectory:

1. Meta conditionally federates with Mastodon instances that sign the deal (allow ads to be pushed, data to be collected, etc)

2. Small/vocal instances reject the deal and defederate.

3. Some large instances do take the deal.

4. Small/vocal instances defederate from the large ones.

5. Large Mastodon instances become pointless as they're isolated from the rest of Mastodon and have no real value over simply using Threads.

6. Large Mastodon instances implode, and the Mastodon fediverse becomes even smaller than it already is.