This article asks a basic question of organizational evolution: When and where will a new organizational form emerge? Using a definition of organizational forms as external identity codes, we focus on two answers drawn from contemporary organization theory. The first holds that formal institutions such as industry associations and standard-setting bodies will result in a taken-for-granted organizational form. The second answer contends that increasing organizational density (number of organizations) will generate a legitimated organizational form. As reported here, a historical case study of the disk array market and its associated technologies finds both arguments limited. Although significant collective activity in association building and standard setting occurs among disk array producers, these have not yet led to an organizational form. Similarly, an observed trajectory of organizational density showing rapid growth followed by stabilization has not yet generated an organizational form. In our view, the diversity of origins and other activities of those organizations operating in this market work against institutionalization of the disk array organizational form. We reason that if firms in the market derive their primary identities from other activities (implying that there are few highly focused firms deriving their primary identity from disk arrays), then the disk array producer identity cannot cohere into a code or form. This conclusion suggests a respecification of the legitimation component of the density-dependent model of organizational evolution.