Background: Open Science is 'the movement to make scientific research, data and dissemination accessible to all levels of an inquiring society'. In the spirit of the Open Science movement, advance publication of protocols for clinical trials is now being advocated by BioMed Central, BMJ Open and others. Simultaneously, participants are becoming increasingly active in their pursuit and sharing of trial- and health- related information. Whilst access to protocols alongside published trial findings has clear benefits, advance publication of trial protocols is potentially problematic for trials of complex behavioural interventions. In this article we explain, with examples, how this could lead to unblinding, 'contamination' between intervention and control groups and deliberate biasing of assessment outcomes by participants. We discuss potential solutions and demonstrate the need for public debate about how this issue is best managed. Conclusion: Triallists may still be underestimating participants' interest in information. This needs to change: joint and open discussions with the public are needed to inform how we should proceed.