Micah Edelson, Tali Sharot, Raymond J. Dolan, Yadin Dudai:
Altering memory in response to group influence may produce untoward effects. For example, social influence such as false propaganda can deleteriously affect individuals’ memory in political campaigns and commercial advertising and impede justice by influencing eyewitness testimony. However, memory conformity may also serve an adaptive purpose, because social learning is often more efficient and accurate than individual learning. For this reason, humans may be predisposed to trust the judgment of the group, even when it stands in opposition to their own original beliefs.
Emphasis mine. The wisdom of crowds and all that.