I'm engaged with a number of clients who need the benefits of a streamlined data infrastructure with multiple systems utlizing the same customer list, product list and so on.  Master data management (MDM) is a term that comes to mind to solve the problems.  Sometimes I'm engaged to organize master data management in the environment and sometimes to look an organization's serious data issues - the ones driving up TCO, keeping the staff busy with repetitive, error-prone tasks and keeping them from getting a full view of customers and products - which leads to MDM as an area to look at for solutions.

I think of MDM as a term to address to a number of real business problems.  It has to do with data quality, sharing data across systems, an enterprise data model, and governance processes and workflows as well as sometimes being a direct data layer to a data-intensive application like CRM.  It's not a product although some products bearing the label provide these benefits.

So, why do MDM?  If and when it alleviates real business pain, solves business problems and enables new ROI-producing functionality.  MDM happens to be a discipline sitting squarely in the sweet spot of modern competitive advantages.