The observed giant planets around other stars are observed to have a range in orbital eccentricities, from circular to very elliptical orbits. The currently favored explanation for this distribution is dynamical interactions among planets after their formation. In cases of very high eccentricities, additional giant planets may actually have been ejected from the system. I will put this model in context for an evolving planetary system, and show that dynamical instabilities are a natural outcome in many cases. In addition, I will explore the role of stable regions in these systems -- could other planets be lurking below the detection threshold in some of these systems?