As I have been expecting this to happen, I finally had the paint on the inside of one rear door erode. It is at the top rear of the door where it contacts the outer rubber strip. Road grit collects between the rubber and the door and, because of the motion of the door relative to the body, eventually 'sands' the paint away. I frequently clean these strips and the rubber strips under the hood for this reason but the grit can collect and sand on the scale of a tankful. I actually had the 3M bra material applied to the inside of the front door but did not expect the rears to be a problem. One more example of the 'Merceds Experience'-are you reading this MBUSA!