Most of us have a specified limit to the amount of traffic our web servers will handle for us. That limit seems very generous until you start looking at image downloads and the bandwidth required. A few dozen users downloading an image that’s one thing. But what if you have an image that dozens of other websites like?
Worst-case scenario: suppose you run a site that gets hold of a picture taken by an Iraqi soldier of an incident that gains a lot of media attention. And suppose you have the exclusive rights to that image. You want to sell it, of course, not give it away, so you don’t post it as a freebie. You may have a downloadable version that others can take away to post on their own website, generally with a link to your site. But your original image is reserved for your use only.
Here’s the problem. Webmasters, often amateurs not really understanding why what they are doing is harmful, want to deliver the best possible image to their own readers. So instead of downloading your free file or linking to your site, they embed a link in their own page that downloads your picture, and only your picture, as part of their own website. This is easy...