THere's absolutely no reason to deface the image with a date/time stamp when all of that info (as well as all the shooting trivia you'll ever want to know) is in the image file (as EXIF data) already. Adobe Bridge and many other programs can display the image and the EXIF data side by side, so you can not only view the image, but see the shutter speed, aperture, ISO, camera serial number and manufacturer, date and time the shot was taken (down to the second), whether or not the flash fired, and many other things.