This chapter has two main aims. First, to argue that the personalisation of online life shapes the communicative and epistemic agency of individual persons and their wider communities. Second, to argue that being shaped in these ways by online personalisation is epistemically risky, so we ought to be warned about these risks. The chapter explores, then, the notion of a specific duty to warn about epistemic risks that target our agency. The fact that many processes and forms of personalisation online strike us as pre-theoretically manipulative is discussed in light of this proposed duty to disclose the epistemic risks of agency-shaping qualities of online life.