A Google Maps Help thread reports that at least one satellite image in South Africa has a weird posterization effect to it.
You can see it yourself at 33°55'7.79"S, 25°35'2.40"E, or Port Elizabeth, South Africa. Here is a picture:
This looks like a heavily posterized image to me, but I doubt that was the case. There must have been some type of interference when the image was captured?
Forum discussion at Google Maps Help.