The arguments I've heard about tracking etc are misguided and don't understand the actual risks.
Firstly, posts on the fediverse are already likely being consumed by advertising platforms like Facebook & Google. It would be trivial for big tech companies to setup relays that act as scrapers.
Secondly, the value in platform's tracking individuals is for advertising. There is no mechanism for these platforms to identify you browsing the we if your instance federated with threads. Your instance won't share cookie sessions etc with threads. It doesn't increase your exposure.
Thirdly, these platforms have the know how to deal with spam and they will be incentivised to share that tech with other federated instances.
Don't get me wrong, Facebook is an evil company. But I haven't heard a decent argument as to why them joining the fediverse is a bad thing. We always have the option to defederate in the future.
Change my mind.
Basically this: https://en.wikipedia.org/wiki/Embrace,_extend,_and_extinguish
First they will add loads of new users and become the dominant instances. Then, they will add their own proprietary features that other instances cannot support. Finally, their extensions become the new de-facto standard, marginalizing the original implementations.
Since Meta has proven itself to be an evil company that does not act in good faith, it is better to not federate with them from the start.
Until I've read your comment I always thought that I would be a good idea but now I'm all against it.