Uniting an eventual 2,800 staffers on one giant floor of a single building, Mr. Zuckerberg takes the idea of a flat hierarchy to its logical—perhaps illogical—conclusion. He and his management team sit in the middle of the floor, placing the maximum number of people at close range. Within the neighborhoods, people can turn or twist their desk clusters to optimize the visual and physical proximity of those with whom they work most closely. The messiness that confounds the visitor thus reflects a hivelike order ruled by interaction.