You've completely missed the point. It's not that Facebook (and by extension, their users) will connect to Mastodon, it's that they will take over Mastodon, seizing all control for themselves, and coopting the existing userbase.

Right now it's a separate product. Just like people know that Twitter is not Mastodon, Threads isn't either. If you want to reach Twitter users, you get a Twitter account. If you want to reach Mastodon users, you get a Mastodon account. Facebook is planning to market themselves as the best way to enter the Mastodon ecosystem. Before long, they will be the absolute dominant server. Then they will have control, because defederation is a weapon they can wield and not vice-versa.

This is not theoretical, either. Google did the EXACT same thing back with Google Talk and the XMPP protocol. And we know how Facebook operates, so we know that this will eventually happen. The only way to stop it is before it starts - Facebook users need to be unhappy (at Facebook) that they can't reach Mastodon users, so that defederation remains their own problem.

(Separately, I agree with you that Lemmy needs to become more accessible to the common user. But simply handing it all over to someone as awful as Zuck is not the way)

Ignoring everything else, they absolutely intend to collect and sell your data regardless of whether you use or interact with anybody from their service:

"Information From Third Party Services and Users: We collect information about the Third Party Services and Third Party Users who interact with Threads. If you interact with Threads through a Third Party Service (such as by following Threads users, interacting with Threads content, or by allowing Threads users to follow you or interact with your content), we collect information about your third-party account and profile (such as your username, profile picture, IP address, and the name of the Third Party Service on which you are registered), your content (such as when you allow Threads users to follow, like, reshare, or have mentions in your posts), and your interactions (such as when you follow, like, reshare, or have mentions in Threads posts).

We use the information we collect for Threads for the purposes described in the Meta Privacy Policy, including to provide, personalize, and improve Threads and other Meta Products (including seamless personalization of your experience across Threads and Instagram), to provide measurement, analytics and other business services (including ads), to promote safety, integrity and security, to communicate with you, and to research and innovate for social good."

https://help.instagram.com/515230437301944?helpref=faq_content

It does either way. As you said defederating threads makes an instance not viable for you. Many people might think that way. This defacto lessens decentralization and increases vulnerability to an eventual takeover.

And defederating threads has the issues you mentioned. Both comes with problems and in the end it might split the fediverse.

Or am I missing something?

if they do, you can just folow them for here right? Or does lemmy.world have less features than kbin.social?