I know there are various plugins out there to help with multisite user management, but we have a policy of avoiding plugins for a) overzealous security policies, and b) interfering with our already heavily-modified WordPress installation (this has bit us before).
Also, simply adding all ~10,000 users to this one blog seems inelegant. That's a lot of new entries in
Is there any filter or action I can intercept to say "if this is blog X, then let any registered user through"? The
admin_init action hook lets me restrict users according to arbitrary criteria, but I don't know how to let them through.