As datafication proceeds rapidly, a large, unwieldy amount of data is available online. In this article, we ask: How valuable is this data, how is it made valuable? To answer this question, we study how online data is endowed with worth in virtual collaboration workshops. Our workshops challenged participants to assert and question the worth of online data – a challenge that participants addressed by using a set of techniques of which we describe collage, hierarchy building, and calculation. Data, we show, gains value through attachment. Thinking with attachment, we foreground affect, materiality, and the situatedness of valuing online data. As ethnographers, we study how data, as haphazard as it comes, is attached to the circumstances and stakes at hand, to ourselves and to other data. Our study contributes a conceptual perspective that attends to the shifting boundaries of the personal and the public, tensions between locality and generality, the role of contiguity, and the limits of combinatorial connectivity.