"It appears that reading a negative review triggers posters' concerns with the social outcomes of their public evaluations, thereby causing them to strategically lower their public ratings. In fact, this bias was limited to posters' public opinions--their private attitudes and thoughts did not differ from those of lurkers," finds Ann Schlosser (University of Washington).
Schlosser's interest in the subject stemmed from her own experience after visiting a local restaurant and then going to the website, Citysearch, to post her opinion: "How might this influence the degree to which I incorporate others' reviews into my own? Past theorizing does not fully address the types of social pressures present in online group contexts like Citysearch. When these social pressures are taken into account, a different pattern of effects is predicted and observed."
Schlosser stresses the very practical applications of this research in consumer research: "Understanding whether consumers accurately post their actual experiences is important because the transmission of product information is a significant aspect of market operations, especially when the informed are weakly tied to the uninformed."
Posting Versus LurkingCommunicating in a Multiple Audience Context. Ann E. Schlosser. Journal of Consumer Research. September 2005.