During the last years our society was often exposed to the coherent information waves of high amplitudes. These are waves of huge social energy. Often they are of the destructive character, a kind of information tsunami. But, they can carry as well positive improvements in the human society, as waves of decision making matching rational recommendations of societal institutes. The main distinguishing features of these waves are their high amplitude, coherence (homogeneous character of social actions generated by them), and short time needed for their generation and relaxation. Such waves can be treated as large scale exhibition of the Bandwagon effect. We show that this socio-psychic phenomenon can be modeled on the basis of the recently developed {it social laser theory}. This theory can be used to model {it stimulated amplification of coherent social actions}. Actions are treated very generally, from mass protests to votes and other collective decisions, as, e.g., acceptance (often unconscious) of some societal recommendations. In this paper, we concentrate on theory of laser resonators, physical vs. social. For the latter, we analyze in very detail functioning of the internet based Echo-Chambers. Their main purpose is increasing of the power of the quantum information field as well as its coherence. Of course, the Bandwagon effect is well known and well studied in social psychology. However, the social laser theory gives the possibility to model it by using the general formalism of quantum field theory. The paper contains minimum of mathematics and it can be readable by researchers working in psychology, cognitive, social, and political sciences; it might also be interesting for experts in information theory and artificial intelligence.