Facebook recently moved me to the new image viewer, which shows a download link below every picture.
With this download link it is possible to download full-resolution original images. I suppose the default is that only the uploader of an image can redownload the original, but I wouldn't mind sharing full versions of certain images directly through Facebook.
On my newest picture, for example,
Right-click > Save as... offers me: 185715_182979465077370_115238648518119_369265_7842179_n.jpg (53KB)
Download gets me:
Is there some way to control who can and cannot download my original pictures?