There's a post doing the rounds which says that Meta's terms and conditions mean they plan to harvest Mastodon users' personal data to target them with ads. Unfortunately that post is misreading the T&Cs, and cherry-picks from a section which is clearly about Threads users, not "third party service users" (ie. us). Here's the full, unedited section.
Note that last part, which details how they use data from here - it doesn't contain anything about ads. Seperating it out like this is the lawyer's way of making it clear that this is what applies to third-parties, and that the above applies to Threads users (otherwise it's just repeating what they already have covered).
Do I trust Meta? Nope! But this is not the smoking gun that it is being portrayed as.
And, as I have to caveat every single time, I 100% support any instance or individual that wants to block, mute, or otherwise not engage with a Meta property.