Through a Graph, Darkly *Abstract:*There is now an overwhelming wealth of data sources (e.g. smart phones) about human social and mobile activities. These resources allow many useful applications: (1) Self-referential uses include: network planning for cellular; offloading and opportunistic network routing; mobile and opportunistic content distribution. (2) Applications include: planning transportation; crowd management; activity-based energy monitoring, and disease epidemic tracking. (3) Commercial use includes: location based advertising; social and mobile based recommendation; social network analysis; urban planning. Much goodness potentially flows from this work.However, all of this comes at a massive cost to personal privacy. To make matters worse, there are trends towards data sharing and publication which (quite rightly) are placing pressure on researchers to share the evidence for their work for reasons of validation, but also (as with medical epidemic (and other) data) to allow as yet unforeseen applications to be run on the real-world datasets. Yet historical data about human movements and encounters is intensively personal. More so even than mere browsing data, which has already caused major furores when inadequately anonymized historical data was released (by AOL).Anonymiszing (hyper)graph data is nigh on impossible according to current understanding.In this talk, I will attempt to lead a discussion about these tensions, and what we might do about this practically. There are several challenges including: culture and conventions for ethical collection of data, and the evolution of the public understanding and informed consent; the technical use of differential privacy, and private preserving queries on such data; alternative ways of building applications that do not require recording such data more than momentarily and locally; and more.