From Abhas Mitra:

Re: Something beyond visible universe detected? (Sept. 23): It may be seen that the explanation for this mysterious flow in terms of inflation is unlikely to be correct: Inflation is supposed to have occurred at t~0, immediately after the big-bang. Then two patches already separated at the time of inflation must be atleast at a mutual separation of ct ~c/H, otherwise the two patches would be part of the same “visible universe”. Since effect of gravitation (or anything else) cannot propagate at a speed further than c, the speed of light, the two distinct patches cannot feel each other’s gravitation. Hence the “Dark Flow” may not be due to gravitational tug of something outside the visible universe.

On the other hand, it is more likely that the flow points out that the visible universe is not really homogeneous and isotropic, on the other hand, it might have a inhomogeneous fractal structrure.