  We show that puzzling recent experimental results on spin diffusion in a
strongly interacting atomic gas may be understood in terms of the predicted
spin diffusion coefficient for a generic strongly interacting system. Three
important features play a central role: a) Fick's law for diffusion must be
modified to allow for the trapping potential, b) the diffusion coefficient is
inhomogeneous, due to the density variations in the cloud and c) the diffusion
approximation fails in the outer parts of the cloud, where the mean free path
is long.
