Mr. Zeldman's classification scheme borrows from literary criticism and views the user's interaction with a web site as an interaction with an man-made artifact or text. Role-based user categorization schemes have several general shortcomings. A role is a schema consisting of a self-view, a structured world paradigm, and a framework of definitions, concepts and rules governing interaction with other roles, agents and objects. Any definition of a role, or assignment of identity based on role, must be very well researched or it risks being superficial and inconsistent. A role assignment that doesn't reflect actual behavior is not helpful.
People play many different roles, often at the same time.
Categorizing users by role must address the determination of the primary role as well as the relative importance of the other roles being played. Role definitions may be driven more from developer projections and expectations than from actual user behavior. Roles that aren't based on observations of real users are not helpful and can in fact be detrimental to the site's usability and its ability to meet its business goals. Role definitions may prioritize mode of interaction over user goals, intentions, or tasks. Users are more likely to be motivated by concrete goals than by abstract philosophies when they surf commerce sites.