While Linked Open Data (LOD) has gained much attention in the recent years, requirements and the challenges concerning its usage from a database perspective are lacking. We argue that such a perspective is crucial for increasing acceptance of LOD. In this paper, we compare the characteristics and constraints of relational databases with LOD, trying to understand the latter as a Web-scale database. We propose LOD-specific requirements beyond the established database rules and highlight research challenges, aiming to combine future efforts of the database research community and the Linked Data research community in this area. Keywords-linked data; Web-scale database; applications.