Fritter is great, but one of the biggest pain points is that it's hard to discover people to follow or that are following you.
Having centralized repositories for discovering people is probably also a bad idea since it would defeat the purpose of being decentralzied and p2p in the first place.
Indexing everyone that signs up is going to be a big load on performance and is probably not a good way forward either.
I propose that when you "follow" a person, that all of the people they're following get indexed too.
The firends-of-friends shouldn't show up in your timeline, but you should still see posts that mention you and should still see their posts in replies to posts on your timeline.
This will make it easy to organically grow your social network through people that you know or that your friends know.
Thus, if a new user joins fritter, if somebody follows, them, they can start interacting with that person's social network and slowly get integrated into it.
In addition, this will make it possible to start indexing who your followers are since it didn't make sense to do it when it would just be a subset of people you follow.