I seriously wish that photographers would watermark all their photos all the time.
Even if it were just better use of tagging on image files. Tumblr does a decent job of preserving tags in files; as do most sites that don’t use imagemagick or the like with default settings to convert images into various sizes.
I’m using Aperture to manage all the images from Deviant/Tumblr hoping that one day I’ll have hundreds of hours where I can just sit and draw from those resources for paintings and illustrations.
I’m betting that thousands of images isn’t that rare a thing. Although Mr. Scoresby could in fact be talking about paper photographs; no idea.