I've been mulling it over for a while, but I've decided to sign the FediPact^1^, pledging defederation for any and all Meta-owned ActivityPub instances (Lemmy, kbin, Mastodon, Threads, etc.).
There may be some real value in exposing such a large audience to the fediverse, but I believe the risks outweigh any potential benefits. Embrace, extend, and extinguish (EEE) is a strategy that companies use to stifle competition and innovation, and I don't want to support Meta in any hostile takeover they may be imagining for the ActivityPub protocol.
Also, the teardown of the leaked Android version of Threads shows that Meta is planning on federating political ads^2^. So yeah, you're welcome.
^1^The FediPact can be found here.
^2^https://tech.lgbt/@[email protected]/110647828827465600