David ... I could heartily agree until I got to the part about the data model being owned by someone outside of IT.  I believe that entities should be owned by organizations outside of IT, but not the data model.  There is the notion of "system of record" where Department A owns entity "John" and Department B owns entity "Mary".  If Department C comes along and wants to create "Fred", but Fred is basically the same as John, then you don't have to fight for what is right.  Department A will do it for you and you can be the peacemaker showing Department C how to get to the data.