Fears about Meta being a bad community actor (careless with data, flooding the zone, etc) seem more immediately plausible to me than the embrace, extend, extinguish scenario.
We need to be ready to both use and improve the community standards and enforcement tools we have.
Keep in mind, though, that if ActivityPub is doing its job, a new entity federating should not create a new attack surface vs the same entity using existing public data.
From @alexis:
https://alexisart.me/@alexis/110568682849646102