Publically viewable ArcGIS Online data that is editable is also editable by the whole public. This is a huge security risk.
Right now, an ArcGIS Online data owner can edit non-editable data through the website. However, if they add the data to ArcMap, the "Create Local Copy for Editing" is greyed out. It would be wonderful to be able to edit AGOL data through ArcMap if you are the owner.
Current (clunky) work-around: 1. Using the website, open the service to editing 2.In ArcMap, log in to ArcGIS Online and add the service 3.Save the map 4.Close the service to editing. 5.The map’s layer will still work, even if you close and re-open the map. 6.Drag this layer to other maps as needed and it will still work. 7.You can only synchronize your edits to ArcGIS Online if you’re logged in as the owner. 8.Do NOT save your map after synchronizing edits or you’ll lose the ability to create local copy.