This paper analyzes the actual use of Mean Opinion Scores (MOS) in the telecommunication industry and looks back on the tremendous evolution that has encountered this sector since subjective test methodologies were standardized by ITU-T (International Telecommunication Union-Standardization). It is pointed out that MOS have severe drawbacks and that test methods should evolve by taking into account valuable inputs from connected research fields such as the psychology of emotions, cognitive science, usability engineering and marketing research.