Someone has explained the basic Embrace, Extend, Extinguish strategy below, but I also want to comment on my own “Embrace, Extend, Consume” idea, as well as the other issues that come with Facebook.
Embrace, Extend, Consume is like Embrace, Extend, Extinguish except the end goal isn’t complete annihilation of the target. Instead of defederating at the endpoint, Meta/FB just dominates the entire standard, and anyone who steps out of line is forced into a miniscule network of others. They can then use this dominant position to buy out or consume large instances, or for example, force data collection features into the standard and aggressively defederate anyone else who doesn’t comply >.<
In this way, they consume the network entirely, which doesn’t necessarily destroy the communities but essentially borgifies them and renders people unable to leave.
The other component specific to facebook is their long and continued history of engaging in what essentially amounts to large-scale psychological manipulation and information warfare towards it’s various goals (money, total domination of human communication, subsuming the internet in countries where the infrastructure is still too small to resist a single corporation restricting it’s content, political manipulation, collection of ever more data, etc.).
They have well over a decade of experience in this, hundreds of times more users, and untold amounts of labour, research and other resources have been poured specifically into figuring out the most effective ways to manipulate social groups via techniques like astroturfing, algorithmic prioritization, and more sophisticated strategies I am not aware of. All backed by data from literally billions of human beings >.<
This means that exposing the Fediverse to Facebook/Meta is essentially exposing us all to one of the most organised and sophisticated information warfare machines that has ever been created. Cutting off the strings (as in the other analogy by @BreakingBad) not only protects from direct EEE/EEC, but also makes it harder for Meta/Facebook to influence, dominate, and consume the conversation here, either by sheer user-mass, or by malicious information warfare (or even unintentional consequences of their algorithms), or by a combination of both.
For hypothetical examples on how this might work - in reality it might be different in specific, these are just illustrative:
Meta/FB could start a campaign (maybe astroturfed) for “user safety”, where they encourage people to distrust users from smaller instances or any user with their instance address marker not on @threads.<whatever their url>
Meta/FB could add “secure messaging” (lol, it’s facebook), but only between threads users. Then they could push the idea that ActivityPub is bad for privacy (the DMs are so just use Matrix ;p, but if you post stuff publicly, it makes sense that it’s public).
Meta/FB could by simple user mass result in most communities being on Threads. People tend to drift towards more populous communities about the same topic, in general, and Threads unbalances the user ratios so much that everyone would just go to those >.< (as opposed to right now, where we have similar sized communities on several large instances, where most people subscribe to most of them)
Meta/FB could use social engineering to push for changes to the ActivityPub protocol that are harder for other ActivityPub servers to implement ^.^, or even ones that are hard for non-proprietary clients to implement.