I'm less concerned about Mastodon itself "scaling" and more concerned about it DDOS'ing tiny sites all over the internet. This problem is still getting worse.
Mastodon encourages a resurgence of blogging, but simultaneously can increase the technical burden of hosting a small blog.
I'm also not that worried about ActivityPub "inefficiency," because at some point, some working group is going to finish a spec for an updated ActivityPub, and servers are all going to slowly migrate.
@mekkaokereke Now this is quite a valid concern, and something that has frustrated me at length.
I actually do wonder what will happen once there’s 100 million active users, and a site goes viral.