  In this paper we investigate the possibility of spontaneous segregation into
groups of traders that have to choose among several markets. Even in the
simplest case of two markets and Zero Intelligence traders, we are able to
observe segregation effects below a critical value Tc of the temperature T; the
latter regulates how strongly traders bias their decisions towards choices with
large accumulated scores. It is notable that segregation occurs even though the
traders are statistically homogeneous. Traders can in principle change their
loyalty to a market, but the relevant persistence times become long below Tc.
