I've consulted for a number of Fortune 500 and 100 companies all of whom have made some kind of effort at creating a "Master" data model even to the point that they'd attempt to have all applications work with a shared database (Imagine the change management issues in that world).
I've seen companies throw millions of dollars at these efforts and still come up short of what they envisioned (although there were in many cases some benefits realized from the effort).
My question here is has anyone seen a truly enterprise-wide master data model implemented and consistently used for anything larger than 100 or so tables?
My instinct leans more toward a message driven/SOA model where individual components were responsible for a subset of data and any component that needs access to that data would go through the appropriate channel. But even then, the "ideal" and reality tend to have a significant difference.