No, the idea is that you block entire instances where the admins are lax about allowing spam or bot accounts. If you run an instance and don't do active modera

No, the idea is that you block entire instances where the admins are lax about allowing spam or bot accounts. If you run an instance and don't do active moderation and just let any putz sign up and post crap, you'll end up getting de-federated and your real users will probably leave (Masto makes it easy to migrate your stuff from one account to another). This is one of the reasons why having lots of instances is a good thing, and one of the risks of Mastodon's federated structure is having a lot of users sign up to one or two big generic instances. I'm hoping that more sites that have existing user communities will start offering Mastodon instances for their already-vetted users. The instance I use (SDF.org) is largely but not exclusively for existing SDF members, and this seems to work quite well. I don't know how the mainline Mastodon server's authentication system works, but hopefully it's reasonably straightforward to plug into an already-existing user database for auth purposes.