The paper addresses the question of how to design for learning taking place on mobile and wireless devices. The authors argue that learning activity designers need to consider the characteristics of mobile learning; at the same time, it is vital to realise that learners are already creating mobile learning experiences for themselves. Profound changes in computer usage brought about by social networking and user-generated content are challenging the idea that educators are in charge of designing learning. The authors make a distinction between designed activity, carefully crafted in advance, and user-generated activity arising from learners' own spontaneous requirements. The paper illustrates what each approach has to offer and it draws out what they have in common, the opportunities and constraints they represent. The paper concludes that user-generated mobile activity will not replace designed activity but it will influence the ways in which designed activity develops. (Contains 1 table.)