The more the better, the less power places like Meta have to change the protocol. For example if Meta pushed for a change to the protocol with just us small guys, we would all push back and say no, but really Meta doesn’t have much to lose if they did it anyway. (We would lose access to them and vis-versa, but it’s Meta after all.)
Now if bigger players are joining like Flipboard, all of a sudden changing that protocol means that they could lose bigger chunks of data, losing flipboard would be a bigger deal.
I’m just surmizing, but I think it’ll be good overall. Legitimizes activitypub more and makes it harder for people to change willy nilly