Self-reported data are regarded by medical researchers as invalid and less reliable than data produced by experts in clinical settings, yet individuals can increasingly contribute personal information to medical research through a variety of online platforms. In this article we examine this ‘participatory turn’ in healthcare research, which claims to challenge conventional delineations of what is valid and reliable for medical practice, by using aggregated self-reported experiences from patients and ‘pre-patients’ via the internet. We focus on 23andMe, a genetic testing (...) company that collects genetic material and self-reported information about disease from its customers. Integral to this research method are relations of trust embedded in the information exchange: trust in customers’ data; trust between researchers/company and research subjects; trust in genetics; trust in the machine. We examine the performative dimension of these trust relations, drawing on Shapin and Schaffer’s discussion of how material, literary and social technologies are used in research in order to establish trust. Our scepticism of the company’s motives for building trust with the self-reporting consumer forces us to consider our own motives. How does the use of customer data for research purposes by 23andMe differ from the research practices of social scientists, especially those who also study digital traces? By interrogating the use of self-reported data in the genetic testing context, we examine our ethical responsibilities in studying the digital selves of others using internet methods. How researchers trust data, how participants trust researchers, and how technologies are trusted are all important considerations in studying the social life of digital data. (shrink)