Abstract In order to incorporate Web 2.0 functionality effectively, digital libraries must fundamentally recast users not just as content consumers, but as content creators. This article analyzes the integration of social annotations ? uncontrolled user-generated content ? into digital collection items. The literature review briefly summarizes the value of annotations and finds that there is conceptual room to include user-generated content in digital libraries, that they have been imagined as forums for social interaction since their inception, and that encouraging a collaborative approach to knowledge discovery and creation might make digital libraries serve as boundary objects that increase participation and engagement. The results of an ongoing case study of a Web 2.0 question and answer site that has made a similar transition from factual to social content are analyzed, and eight decision points for digital libraries to consider when integrating social annotations with digital collection items are proposed.