  We use a simple model to describe the nonlinear dynamics of a dense two
dimensional dipolar exciton gas. The model predicts an initial fast expansion
due to dipole-dipole pressure, followed by a much slower diffusion. The model
is in very good agreement with recent experimental results. We show that the
dipole pressure induced expansion strongly constrains the time available for
achieving and observing Bose-Einstein quantum statistical effects, indicating a
need for spatial exciton traps. We also suggest that nonlinear ballistic
exciton transport due to the strong internal dipole pressure is readily
achievable.
