A problem for non-Facebook ActivityPub-compatible services.

It's really difficult for apps to support a feature for any server. It's far more complicated than it is to support it for one service.

So if there's one service with far more users than all the others combined, developers will just support that service.

There is a solution but it requires cooperation and trust, and a little bit of centralizing.

I thought I should say this before FB enters, while there's time to act before.