From the pictures, the smudges appear to be underneath the display and only appear for a short time (since the location varies). Is this correct? Also, do you remember what the weather/room conditions were when this occurred? I'm wondering if it could be heat or humidity related. I haven't heard of these smudges before, but you should definitely head to an Apple Store for an under-warranty replacement--even if the smudges rarely occur. I say that because there may be something wrong with the display or how it is attached, and if this is the case the display may malfunction in the long run.