Advances in location-sensing technology, coupled with an increasingly pervasive wireless Internet, have made it possible (and increasingly easy) to access and share information with context of one’s geospatial location. We conducted a four-phase study, with 27 students, to explore the practices surrounding the creation, interpretation and sharing of map annotations in specific social contexts. We found that annotation authors consider multiple factors when deciding how to annotate maps, including the perceived utility to the audience and how their contributions will reflect on the image they project to others. Consumers of annotations value the novelty of information, but must be convinced of the author’s credibility. In this paper we describe our study, present the results, and discuss implications for the design of software for sharing map annotations.