The utility of twitter, facebook and reddit is their ubiquity. They each, in their own way, became the place you go to find [thing], and federated services will never have that. Discovering mastodon users who aren’t already followed on your instance is hard. Discovering lemmy communities that aren’t already followed on your instance is slightly easier. They’re never going to show up in Local if they’re not local, and they’re never going to show up in All if no local subscribes. Decentralization, even with federation, works against virality, and if there’s not a steady flow of content, then few people bother to sign up.

The instances get exponentially more useful as they get larger, but the costs of operation also get exponentially larger. If lemmy catches on, instances will absolutely grow beyond donations.