Whenever individuals or groups rate, judge and decide something, there is the possibility of cognitive biases getting in action and skew the actual ratings, judgements and decisions systematically in one direction. I think its important to be aware of such cognitive biases for not getting manipulated so easy by your brain heuristics and maybe people who are manipulating conscious or unconscious in a given sitationsituation. The main researchers in this topic are Kahneman & Tversky with many publications since the 1970s.
It follows a table with some of the most important biases categorized ad-hoc by myself in the following categories: individual thinking, individual rating, individual decision-making, group thinking, group rating, group decision-making...