I dont actually believe that many understand ERDs. Would like to see a survey on what people do know, and the extent.

Last few companies I have worked at none of the DBAs or developers understood what a ERD was. Blank expressions have been the norm. Suggest it as a method of resolving a dispute on the suggested relationships of the schema and they have often not understood or refused it as the "code knowns"; yeah then why the discussion in the first place?

My issue with the diagramming tools that MS provide is that they have such basic notation.