I've put a blog entry on the Brand Science Institute site about some work in this area.
The work begins with Bart Bronnenberg (and his colleagues Dhar and Dubé), who note that there's often substantial variation in who the leading brands are in a category. For example, Folgers might be the larges coffee in one market, while Maxwell House is the largest in another. These differences are large and persistent.
I focused on WHY these differences are persistent. For more, see the BSI link.