I came across this article from John Griffiths on the SigmaSurveys blog in which he stresses the importance of anonymity for participants in marketing research.
Here are two reasons for anonymity that stand out from the article:
The first is ethical ‘ that a client company might treat a respondent differently and in a way that was prejudicial to the interests of that respondent if it were able to identify them. The second is methodological ‘ respondents would not be forthcoming if they were asked the same question directly by a client.
Take a couple of minutes to read this informative article.
View the PDF of the article