Extra Easy way to know what uses the data-block

1. Use a material on several objects,
2. click the X aka delete button on the material
3. blender: yeahhhh it’s still in use elsewhere, i’m going to keep it… go figure out on your own where it’s used.

from : devtalk.blender.org/t/blender-2-8-user-interface-design/505/2

With the current GUI and python API, it is fairly easy to find "What the data-block uses" while it is very difficult to track "What uses the data-block".

AND it is very frustrating. I believe that all data-blocks in blender should have a reference to its users which is accessible from our beloved out-liner.