We reflect on long trials of two prototype social media systems in rural South Africa and their biases towards certain communication practices on information sharing. We designed the systems to assist people in low-income communities to share locally relevant information. Both involve communal displays, to record, store and share media, and users can transfer media between the display and their cell-phones. MXShare, which we report for the first time, also enables real-time, text-based chat but AR enables sharing only audio files asynchronously. Both systems were located at the same sites for community communication and co-present oral practices effected media recording and sharing. Their use reinforced differentiations in sharing information between older and younger people. We argue that designing social media systems to widen information access must respond to complex interactions between social structures and genres of communication.