I have two separate identities on 2 instances. One has only 40 members, on which I am a moderator, which is a subset of a forum's community and both being funded with donation and a yearly fee to be allowed to post ads in the local marketplace. The other one is much larger but runs on a single Hetzner VPS and is also funded with donation. Admin recently switched registration to manual approval, probably to control and limit the amount of accounts.
If I ever have to run my own fediverse/activity pub server/community, I would definitely put a limit on the active accounts I would serve and have an housekeeping rule to clean up inactive profiles.
If you have a user that starts following 10k user in a short time, you have a spam bot and not a user.
The fediverse is not made in such a way that your social circle grows quickly. You usually starts by following people on your own instance, then people whose content is boosted by them and it only happens slowly and gradually.
The users it finds aren't necessarily ones you've interacted with -- I know from running single server instances
I stopped running an instance because of this functionality. I was running Mastodon on my home Internet and quickly became concerned about the image content it was downloading from users I hadn't interacted with, while I wasn't monitoring the server
There is a LOT of lolicon content on the Fediverse and NOTHING is worth the risk of running a server that might download material that's considered to be CSAM to my local computer while it is unsupervised
So you have to worry about both the quantity of content it downloads and what that content is
As an admin: no thanks.
Your statement is a hint to the problem.
From what I find on the Internet, you can still communicate/follow people on other servers without getting their timelines. It's just that the default setting is to pull everything from those relays and you need to disable it.
With that setting, you'll get everything people you follow on other instances, but not more. The "Federated timeline" tab will remain empty.
I'm more genuinely worried about Mastodon and other parts of Fediverse forgetting why they were made in the first place. They are made as a network for the users, not for selling ads. They can make every decision with the users wellbeing in mind and this is incredibly powerful in today's world. (if they stick to that, I'm sure they'll find a lot of success)
Selling out as the author seems to suggest would make them into a boring Twitter clone as far as I can tell.
[1] not only mastodon.social, also others like mstdn.social, fosstodon.org, and more -- if not, check with your instance maintainer :)
Correction: Most of the author's complaints are about the cost and complexity of running a large instance. I know people running their own instances, with less than 10 users, yet they are happily tooting with people in other instances. They aren't missing out on something that I, on one of the largest instances, have.