They do weird things but it's probably not hurting your returns. I'm not so sure. The financial system is a nonlinear dynamical system. The hallmark of such sy

They do weird things but it's probably not hurting your returns. I'm not so sure. The financial system is a nonlinear dynamical system. The hallmark of such systems is that small local perturbations can lead to very large changes in system-wide state. High-frequency trading vastly increases the number of small perturbations, and while most remain local, there is a finite probability that some will percolate upward in scale. So micro-scale trading may increase our exposure to catastrophe.