I wouldn't say "most". According to that site, of the 4880 instances list, 1909 are close and another ~300 are invite-only.
> it's expensive to run this
As the hype about Mastodon spiked after Musk bought twitter, I looked at it to see if I could set up an instance, just to experiment. I'm an experienced programmer and systems administrator. After perusing the requirements and installation process, I decided that it was too much work for a little one-person experiment. This is why I ask about who is running instances. Yes, I had a strong hunch it would be all nerds, but I didn't expect it to be require so much sophistication and outlay. One very dedicated person could certainly set up and run an instance, but most likely any instance of moderate popularity is going to require a team.
> it's expensive to run this
As the hype about Mastodon spiked after Musk bought twitter, I looked at it to see if I could set up an instance, just to experiment. I'm an experienced programmer and systems administrator. After perusing the requirements and installation process, I decided that it was too much work for a little one-person experiment. This is why I ask about who is running instances. Yes, I had a strong hunch it would be all nerds, but I didn't expect it to be require so much sophistication and outlay. One very dedicated person could certainly set up and run an instance, but most likely any instance of moderate popularity is going to require a team.