The ever-growing datasets of user activity traces promise to o er captivating insights into human phenomena. Yet, these datasets are more than just an observational tool. The insights derived from them are increasingly being used to drive policies, to shape products and services, and for automated decision making. It is therefore important to understand the limitations around their use, especially when they are used to tackle signi cant societal challenges, such as humanitarian crises, climate change, minority issues, hate speech, and health { social good applications that we will be covering in this talk.