The aim of the paper is to follow long-term tracking of the characteristics and behaviours of survey respondents who claim to participate in online surveys. This report outlines the different ways in which this segment of the population differs from the remainder of the population who are active online. We demonstrate that there are some differences in the demographic profiles and these are routinely accounted for when weighting results derived online. However, we demonstrate the much wider differences in behaviour and attitude that remain after accounting for demographics. As a result, we propose some approaches that might be used to mitigate the inherent dangers involved in relying on online research information when seeking to estimate the overall scale of a market opportunity.