There is much hyperbole associated with de-duplication. The purpose of this document is to help readers distill the essence from the hype, as the basis for sound decision-making. This document is not intended to judge what is good or bad, right or wrong. The primary focus is educational, providing a background on the principles of de-duplication and recommendations to consider in planning an evaluation of de-duplication solutions. A key goal is to identify the right questions that should be asked in the context of the evaluation of de-duplication solutions.