Since the earliest days of world exploration, maps have told compelling stories to people who may never see the places depicted. Topographical lines on paper only go a small way to recreate the traveller's experience, however, and the rest depends on the viewers' imagination. Now, personalized and interactive maps are stretching those ...

''Welcome to the age of the crowd,'' wrote Jeff Howe in The Rise of Crowdsourcing (2006). In coining the term crowdsourcing, Howe pointed to the rise of the open-source software movement; to the success of user-created Wikipedia; and to profitable businesses like MySpace and eBay ''that couldn't exist without the contribution of users.'' Howe put ...