In rare cases of deep and long-lasting friendship and mutual trust, the expression of negative feedback helps individuals to assess and improve their performance and their selfhood. More often, however, criticism is an act of aggression designed in some way to block or damage the recipient. It is especially powerful used in a social context, in which criticisms based on personal preferences and those based on group policy become mingled, and the mass media expand a passing comment into a "story".
The 1988 American presidential campaign used criticism as the primary strategy by which candidates attracted the attention of the electorate.
For every action, there is an equal and opposite criticism.