Modern online advertising often employs different kinds of social influence features, which are likely to be experienced differently by different users, such as individuals with different levels of advertisement (ad) scepticism. In this study, we focus on these differences by examining (1) how different kinds of personality and demographic traits affect ad scepticism, and (2) how ad scepticism, in turn, affects the user experience of four different kinds of social influence features. By using data from 628 online shoppers, we find ad scepticism to be affected by four out of the Big Five personality traits as well as age and education. We also find ad scepticism to negatively affect user experience, with a stronger effect in the case of social pressure than social proof features. These novel findings promote our understanding of the antecedents of ad scepticism and of the potential risks of employing social influence features in online advertising.