Interpretations of the concept of "affordances" in HCI are becoming increasingly diverse, extending well beyond the original Gibsonian meaning. We discuss some of the key analyses of affordances in HCI research and make three related claims. First, we argue that many current interpretations of the concept are essentially incompatible with Gibson. Second, we hold that the Gibsonian concept of affordances, conceptualized as interaction between animals and their environments, provides some important insights, but is, in the end, of limited relevance to HCI research. Third, we call for adopting a mediated action perspective on affordances as an alternative to Gibson's ecological psychology. We outline a view of technology affordances as possibilities for human action mediated by cultural means conceived as a relational property of a three-way interaction between the person, mediational means, and environment. We conclude with a discussion of prospects for future conceptual and empirical explorations of the meditational perspective in HCI research.