* create_active_users:
  Controls whether new user accounts are created as 'active'; accounts
  that are not marked as active will not be able to log in, and will be
  automatically logged out if they're already logged in.

* allow_registration:
  Allow or disallow creation of new user accounts. Any attempts to
  access the registration page will result in an error message.

* allow_anonymous_uploads:
  Allow or disallow uploading of files by anonymous (not logged in)
  users. Combined with either allow_registration or create_active_users,
  this will effectively create a private filebin where the admin must
  explicitly create or activate new users.