  We present a financial market model, characterized by self-organized
criticality, that is able to generate endogenously a realistic price dynamics
and to reproduce well-known stylized facts. We consider a community of
heterogeneous traders, composed by chartists and fundamentalists, and focus on
the role of informative pressure on market participants, showing how the
spreading of information, based on a realistic imitative behavior, drives
contagion and causes market fragility. In this model imitation is not intended
as a change in the agent's group of origin, but is referred only to the price
formation process. We introduce in the community also a variable number of
random traders in order to study their possible beneficial role in stabilizing
the market, as found in other studies. Finally we also suggest some
counterintuitive policy strategies able to dampen fluctuations by means of a
partial reduction of information.
