I'm trying to figure out why giving only the ISO is useful information (as opposed to also citing aperture, shutter speed and exposure compensation).
I look at the current home page photo, "Crescent Moon, Antarctica," and the lighting conditions don't appear to be unusual. According to the EXIF the focal length is 200mm, ISO is 200, aperture is f/5.6, the shutter is 1/400 and the exposure comp is -2/3rds stop.
All of the settings make perfect sense, especially as the ship was moving when the frame was captured.
Citing ISO only seems arbitrary, but I'm not sure that adding aperture and shutter speed info really adds anything useful, either. It's only in the context of the conditions under which the frame was captured that we understand why the camera settings were chosen.