Originally posted by CarlG Just a note -- post low resolution pictures if that still makes your point. Those are less interesiting for these abusers.
Unfortunately, even low-res is often enough for (for example) commercial web use, printed posters, T-shirt etc. Most of the images I've posted on flickr are no bigger than 1024px on the wide side, but several abusers have still found ways to put them to use.
For instance, I was at a local club recently and found one of my images decorating a stubby holder [beer can cooler]. For that kind of use they don't need a full-res image. No one had ever asked me about using the image, of course.