Even a centralised planning organisation can only do so much against money and exploitation here. We've seen this already with the W3C and various companies dominating planning and uptake of web standards.

I'm of the opinion that prevention measures needs to be built into the system, but I dont know what form that might take.

I guess a lot depends on how many of Facebook/Instagram's users sign up for Threads, but it's pretty likely to be exactly the opposite scenario...

The fediverse is a small, friendly, relatively peaceful country town, and it's about to be directly connected to Tokyo or New York.

Which do you think is going to end up having more of an impact on the other?

No corporation would want to enter a nascent growing space to play around in that sandbox. Play nicely with everyone and even offer some cool new toys that excite everyone enough to try their stuff out. Then that corporation would never invite everyone to play inside their yard with the awesome stuff, inviting everyone everyone knows to the party; then locking the gates at midnight and shut off all the toys to everyone outside the gate. Not once had this ever happened in the tech world.

They want to do the same thing Google did with Jabber/XMPP. Microsoft's: Embrace, Extend, Extinguish.

Google with their Google Talk did exactly that. They introduced their own instant messaging. Mamy XMPP users (including myself) convinced friends to join Google Talk. Once it picked up they first broke communication (it only worked one way, you could see GT people online, you could see them messaging you, but your messages never arrived) eventually they defederated completly. I still feel being used.

Facebook knows that it is tough to bootstrap community when there are no users in it, and they want to do exact same thing.

I think it will be both. Accounts created with Threads will have their own walled garden but will have the option of interacting with other fediverse communities.