I have a 2.4 GHz Intel Macbook Pro and I've started to notice small circular black marks near the edge of the upper left corners of my computer. They're about a centimeter in diameter and black. I swear they appeared overnight. My computer spends a lot of its time in my backpack in a padded macbook sleeve. I've dropped my backpack a few times, but I don't see how that would result in these little 'cigarette burns.' I've attached photos. Should I be worried? Any idea what repair will cost? What do you all think?