It will be a pixel peeper xmas after all: "There has been some speculation about whether it shows up mostly in JPEGs or mostly in RAW conversions and whether it depends on which RAW converter you use and if you have noise reduction turned on. However in both JPEG and RAW images produced by several different RAW converters, the black dots to appear to correlate with (typically) a small block of pixels immediately to the right of an overexposed region. The fact that they always appear immediately to the right of the bright area (with the camera held horizontally) may be related to the way in which the data is read from the sensor array (in horizontal rows, perhaps from left to right?). It's not clear if the black dots are hardware or software related"  Link