Technologies associated with the second-generation of the World-Wide Web enable virtually anyone to share their data, documents, observations, and opinions on the Internet. In less than three years, mapping platforms such as Google Maps have sparked an exponential growth in user-generated geographically referenced content. However, the “serious” applications of Web 2.0 are sparse and this paper assesses its use in the context of collaborative spatial decision-making. We present an online map-based discussion forum that enables Internet users to submit place-based comments and respond to contributions from other participants. We further use the geographic references in a thread-based master plan debate for a university campus to simulate this debate in the map-based forum. This allows us to demonstrate how the online map provides an overview of the status and spatial foci of the debate, and how it can help us understand the spatial thought processes of the participants.