"Secrecy removes biases. As @kidmercury says, it's pretty clear with voting. But generally, look at Facebook like's. Since they're so public, it's now pretty clear that they say more about the person liking (and its relationship with the poster) than about the content itself. So we have conflicting signals here. A like incompases 2 things : - the fact that the content is interesting to me - the fact that I want to be known that I liked a post. It's not always easy to asses the proprotion of these 2 signals. Secrecy is a way to remove the 2nd one. It's also one of the rationales behind 'anonymous resumes' or 'blind tests' in the food industry." - Julien