By far the most fascinating and profitable subject of predictive algorithms is the human actor. The capacity to predict human preferences, responses and behaviours offers endless possibilities for science, commerce, politics and regulation, and promises convenience and efficiency that further private and public interests in equal measure. There is nothing inherently new about the attempt to predict buying choices, political leanings and likely votes of individuals and groups, the probable effectiveness of medical treatments, likely defaults on loans, the chance of fraudulent insurance claims or of reoffending. Yet, the capacity to 'know' the individual and the group, and to predict their constitution and behaviour has witnessed a sudden upturn of unprecedented scale. The rise of network society and smart technology is generating endless trails of personal data, finely pixelated digital footprints, that are aggregated into big data setsthat involve large collections (volume) of real-time (velocity), diverse and relational personal data (variety) 1about virtually all aspects of human life from shopping, food and entertainment preferences, friendship networks, romantic attachments, social activities, health concerns, physical movements, driving behaviour or sporting activities, to biometric data, such as voice, face, gait or keystroke, or physiological data on heart rate, blood pressure or sleeping patterns. These data sets, when mined by algorithms, can reveal significant patterns and correlations and, ultimately, produce knowledge about the group (e.g. behavioural trends, economic activity, delinquency, spread of disease, political trends, etc. 2 ) and about the individual (e.g. educational level, social status, political leaning, sexual orientation, emotional states and psychological vulnerabilities as well as predilections for activities and movements). This knowledge then lies at the disposal of the private sector and government to be used for a wide range of purposes, implemented through 'personalised' services, treatments and regulationsome beneficial, some harmful, but mostly a mixture of both.