We’re not used to thinking of “groupness” as a specific category—the differences between a college seminar and a labor union seem more salient than their similarities. It’s hard to see how Evan Guttman’s quest for the return of the mobile phone is the same kind of thing as the distributed documentation of the Indian Ocean tsunami. But like a chain of volcanoes all fed by the same pool of magma, the surface manifestations of group efforts seem quite separate, but the driving force of those eruptions is the same: the new ease of assembly.