In a large organisation with more and more web maps and web apps being created, it is hard to keep track of all the places a data layer may be being used. Therefore, you may delete or un-share a layer and disrupt a web map / app functionality without even knowing!
My idea is for a warning message to appear before you delete or un-share an item ideally stating all the content that layer is present in or at least that it is in use elsewhere.
Yes you can delete protect items but for a layer a GIS admin has shared with all Portal user's, how are we to know who is using what layer in their web maps?!
This idea came to mind recently when our general-use mapping app for the entire organisation (shared with 'Everyone' on Portal meaning you are not required to be a named user to view) stopped allowing anonymous user's to view because a layer sitting behind a custom locator had been un-shared.
You would expect this just to produce the normal error message you get as a named user '...this layer cannot be added to the map...' but instead any anonymous user was denied access to the whole application re-directing them to the sign-in page. If a warning message had appeared when un-sharing the layer, the issue could have been resolved before locking user's out of the app!