In FEP 1b12, that is what occurs (most of the time) - as soon as an instance has a dozen users their interests will be varied enough that almost every active community in the threadiverse is subscribed to and they'll be receiving almost all the traffic.

It works out ok at our current scale (small).

@evan At Friendica we have a third way. When configured, we distribute posts to other servers that subscribed to the hashtags that the item contains.

But anyway: I would like to have got something like the AppView in the Atmosphere. Means: not a dumb relay but something like tags.pub, but much more sophisticated.

Another possibility is that when someone asks to have their content shared, that will result in a few Follow requests, which does result in their future content being distributed to other servers (and public content goes to Fediverse and hashtag feeds).

So, it seems like the sharing is what got the distribution going, even though it is indirect (sharing causes following causes appearing in the Fediverse feed).

In the streams repository a few years back, we implemented a mechanism where "site actors" could follow each other, and this would result in sharing local public content with selected other sites, regardless of personal connections between actors. This scales so you can build small or large "clusters" or cooperating servers. The keyword being that this is server sharing which is "consent" based.

There was little or no interest in this ability from anybody, so the feature languished. I think it's still implemented, but there's no motivation to pursue it further. I'll just mention it if somebody else feels like dying on hills today.