When users share filters or Dashboards with 'Everyone' the following message is displayed:
"Sharing with everyone will make this visible to users who are not logged in."
But this leads them to believe that only jira-users not logged will be able to view and not every person that manages to find the 'Manage Filters' or 'Manage Dashboards' link.
Also, on the 'Manage Filters' or 'Manage Dashboards' screen they are displayed as 'Shared with all users' which strengthens the belief that it is only shared with internal users.
It would be better to change this labels to 'Share with world' to enforce that everyone will have access to the filters.