Over the past years, psychology has seen a remarkable move to increasing research transparency, following several high-profile cases of scientific misconduct and the realization that reproducibility of psychological research findings may be disappointingly low. Taking from exact science disciplines such as experimental physics, there is increasing support for public sharing of empirical data, with some researchers even arguing that public data sharing should be a requirement for publication. Indeed, the principle of data transparency is a core value in science. However, in psychology and cognitive neuroscience, researchers work with human subject data. This makes that data sharing is subject to legal and ethical restrictions. Here we discuss the legal and ethical implications of public data sharing, as advocated by several authors. We conclude that large scale public sharing leads to inevitable legal and ethical problems with participant privacy, especially in the light of continuous technological developments. What might be ‘anonymity’ today could be become personal data tomorrow.