The roadmap of the Smart Grid project includes exploiting the intrinsic elasticity of electricity demand in the future, to make it responsive to the near term cost of supplying generation. This would curb costly peaks of demand and allow for a greater penetration of renewable energy sources. The mechanisms serving this purpose are referred to as Demand Side Management (DSM) and Demand-Response (DR) programs. While it is clear that DSM and DR will be indispensable to loosen the control over the generation and decrease the reserve requirements, there is much debate on what is the right architecture for DSM and DR programs. In this paper we discuss current trends that are being considered as candidates for DSM and DR and critically compare them, outlining research directions that should be pursued in the future to overcome this dilemma.