In recent months there has been an explosion of interest in using the Web to create, assemble, and disseminate geographic
information provided voluntarily by individuals. Sites such as Wikimapia and OpenStreetMap are empowering citizens to createa global patchwork of geographic information, while Google Earth and other virtual globes are encouraging volunteers to developinteresting applications using their own data. I review this phenomenon, and examine associated issues: what drives peopleto do this, how accurate are the results, will they threaten individual privacy, and how can they augment more conventionalsources? I compare this new phenomenon to more traditional citizen science and the role of the amateur in geographic observation.