This article examines whether social media users can validly consent to their own use of social media. It argues that, whether or not social media use is analogous to public health interventions, there is an obligation to provide users with information about risks and benefits, and absent that provision, there is no valid consent. Many or most users, in any event, do not have the capacity to consent, according to the criteria for capacity articulated in the ‘four abilities’ model: the ability to express a choice, the ability to understand the facts pertinent to the decision in question, the ability of a subject to believe that the information applies to them, and the ability to reason—in the sense of being able to consider and weigh (with reference to the patient’s own concerns, circumstances, and values) the main possible outcomes of the decision to opt for the intervention and the decision to opt not to undergo it. Even if an individual social media user is capacitous according to these criteria, many will fail to be judged capacitous if (as it is argued should be the case), a further criterion, identified by Jennifer Hawkins must be satisfied, namely that the individual can look after their own interests at least as well as most other people can. It follows from this consideration that not only can regulation of social media (in the form of a ban) be justified under Mill’s harm principle, but that non-regulation cannot be justified.