Small businesses can individually refuse to do business with the big shopping mall -> add threads to the block list ('defederate' them)
The big shopping mall is not allowed to put their building at the public square -> threads is not allowed to use ActivityPub
The first statement is totally ok and a lot of instances do this. However, similar like shopping malls it can pose a challenge for small businesses to stay competitive, while categorically refusing business with the big actor. The second statement would require the towns construction committee to not give the shopping mall a license to build. However, this construction committee is a centralised power and not in the design of ActivityPub.
I do not like threads and see them as a potential threat to what we have here. Exactly because it could become harder to stay competitive while refusing them. But i don't see much that we can actively do.