Marketization, which is gradually expanding the empire of commodities and imposing the financial world’s modes of evaluation on more and more sectors of activity, acutely raises the question of the role of markets in contemporary societies. The debates surrounding marketization have generated a set of contrasting arguments corresponding to different attitudes towards marketization: markets being synonymous with efficiency and democratic standards, markets as machines which destroy the social fabric, or markets perceived as fragile institutions threatened by conservative forces. The objective of this chapter is to contribute to changing the terms of the debate, in particular through reconsidering the way in which market and competition are closely associated. A thorough examination of the notion of market competition leads to a distinction of two ways of describing markets, depending on the role played by product innovations. In interface-markets, innovation strategies aim to reduce competitive pressure, while in market-agencements they are the expression of competition itself. In the former, the definition of market goods is secondary, whereas in the latter it is at the heart of the confrontation between economic agents. Empirical research on the innovation process confirms the greater realism of the market-agencement conception and leads to a new view of marketization and its implications. The competitive dynamics of market-agencements, which makes the establishment of new bilateral transactions and of product innovation the dominant rule, results in the constant expansion of the market sphere. The marketization process is thus at the core of markets’ functioning.