Spatial technologies and the organizations around them, such as the Standby Task Force and Ushahidi, are increasingly changing the ways crises and emergencies are addressed. Within digital humanitarianism, Big Data has featured strongly in recent efforts to improve digital humanitarian work. This shift toward social media and other Big Data sources has entailed unexamined assumptions about technological progress, social change, and the kinds of knowledge captured by data. These assumptions stand in tension with critical geographic scholarship, and in particular critical GIS research. In this paper I borrow from critical research on technologies to engage three important new facets of Big Data emerging from an interrogation of digital humanitarianism. I argue first that within digital humanitarianism, Big Data should be understood as a new set of practices, in addition to its usual conception as data and analytics technologies. Second, I argue that Big Data constitutes a distinct epistemology that obscures many forms of knowledge in crises and emergencies and produces a limited understanding of how a crisis is unfolding. Third, I argue that Big Data is constitutive of a social relation in which both the formal humanitarian sector and “victims” of crises are in need of the services and labor that can be provided by digital humanitarians.