In today's media environment, information is not simply passed from producers to consumers, but is mediated by participants of new media cultures, including information on sexual health. In focus groups held in Sydney and regional Australia in 2011, we asked young people aged 16-22 about the potential for sexual health promotion via Facebook and other social media. Our findings point to the complex ways in which young people use social media, and the unlikelihood of traditional take-home sexual health messages having traction in social media spaces. Five key aspects which emerged were: the participatory culture of social network sites; the stigma of sexual health, especially sexually transmitted infections (STIs); young people's careful presentations of self; privacy concerns; and the importance of humour in sexual health messaging. Fears of bullying and gossip (or 'drama') were also likely to prevent the dissemination of sexual health messages in this environment. However, humorous online videos were noted by participants as a significant way to avoid stigma and enable the sharing of sexual health information. The young people in our study were interested in sexual health information, but did not want to access it at the cost of their own sense of comfort and belonging in their social networks. Any sexual health promotion within these sites must be understood as a site-specific intervention.