Through ethnographic research, we document therise of personal social networks in theworkplace, which we call intensionalnetworks. Paradoxically, we find that the mostfundamental unit of analysis forcomputer-supported cooperative work isnot at the group level for many tasks andsettings, but at the individual level aspersonal social networks come to be more andmore important. Collective subjects areincreasingly put together through theassemblage of people found through personalnetworks rather than being constituted as teamscreated through organizational planning andstructuring. Teams are still important butthey are not the centerpiece of labormanagement they once were, nor are they thechief resource for individual workers. We drawattention to the importance of networks as mostCSCW system designs assume a team. We urge thatdesigners take account of networks and theproblems they present to workers.