After clarifying the notion and different areas of the (digital) "public domain" the paper engages in discussing literature on its relevance for society in general and economic innovation in particular. The effectiveness of the utilization of these abstract potentials however depends on the respective public domain regulation. In this context, the paper distinguishes different regulatory modes and arenas in both copyright and patent law, thereby focusing private regulatory initiatives such as Creative Commons or Biological Open Source (BiOS). In the last section, the paper presents open research questions and makes some preliminary suggestions for potential research strategies.