https://ploum.net/2023-06-23-how-to-kill-decentralised-networks.html
Many of us do not trust Facebook and anything it is associated with or swallows up.
EDIT:
"Instagram head Adam Mosseri said "
““Soon, you’ll be able to follow and interact with people on other fediverse platforms, such as Mastodon. They can also find people on Threads using full usernames, such as @mosseri@threads.net.””
“We’re committed to building support for ActivityPub, the protocol behind Mastodon, into this app. We weren’t able to finish it for launch given a number of complications that come along with a decentralized network, but it’s coming,” he said.
“If you’re wondering why this matters, here’s a reason: you may one day end up leaving Threads, or, hopefully not, end up de-platformed. If that ever happens, you should be able to take your audience with you to another server. Being open can enable that.”
There’s no way to inject ads into your feed, except possibly by the admin of your own instance. Meta, or any other actor, could hypothetically use a bunch of bots to promote regular posts that are secretly ads throughout the Fediverse, but that would lead to them getting defederated very quickly by everyone else.