Pluralistic ignorance
In social psychology, pluralistic ignorance is a situation in which a majority of group members privately reject a norm, but go along with it because they incorrectly assume that most others accept it. This is also described as "no one believes, but everyone thinks that everyone believes". In short, pluralistic ignorance is a bias about a social group, held by the members of that social group.
Rational irrationality
The most famous theory of democratic failure is public choice theory. The theory, developed by James Buchanan, Gordon Tullock, and others, relies on rational ignorance. Voters have a very small probability of influencing policy outcomes, so they do not put much effort to stay up-to-date on politics. This allows special interests to manipulate the political process and engage in rent seeking. A key idea of public choice theory is that many harmful policies have concentrated benefits (experienced by special interests) and diffuse costs. The special interests experiencing the benefits are willing to lobby for the policies, while the costs are spread out very diffusely among a much larger group of people. Because these costs are diffuse, the people bearing the costs do not have enough at stake to lobby against the policies.