MikaMikem replied on the forums with:
"Um? This is a cool optical illusion and it works because... If you look at the circle of rhombus' as two concentric circles with the top and bottom of the rhombus' as the circle border it is obvious that one circle will be bigger than the other. Because the outer circle is larger the gap between rhombus' is going to be larger near the outer side of the circle as apposed to the inner side. Because you move closer to the circle the gap gets smaller relative to your vantage point. Because the outer edge of the rhombus circle gets smaller faster the outer edge appears to move and as the rhombus is facing a certain direction so does the movement you percieve. Now while that seemed extremely scientific it was a flat out guess and could be entirely wrong so don't take my word for it. I would love to see someone post a good solution to this cause I really do want to know why you see it moving."