Digital displays are heralded as a transformative medium for communication. However, a known challenge in the domain is that of display blindness in which passersby pay little or no attention to public displays. This phenomenon has been a major motivation for much of the research on public displays. However, since the early observations, little has been done to develop our understanding of display blindness – for example, to identify determining factors or propose appropriate metrics. Hence, the degree to which developments in signage form, content, and interaction address display blindness remains unclear. In this paper we examine and categorize current approaches to studying and addressing display blindness. Based on our analysis we identify open questions in the research space, including the impact of display physicality and audience differences, relationships with other observed effects, the impact of research interventions, and selection of appropriate metrics. The goal of this paper is to start a discussion within the community on the topic, and to inform the design of future research.