I recently found out one of my website's content (articles) has been copied in various websites and blogs across the web. Some have provided a backlink to my website, which is fine with me, fair exchange I'd say. But others, have not.

I found out about one of these guys because they kept the links to the images on my server intact. They copy/paste the article, and the images are still served from me.

I do not want to do something drastic, like replace the images with soft pornography or something equally inappropriate, and get them embarrassed. I'd rather want to take advantage of the situation and get more backlinks to my website. When they copy/paste stuff on WYSIWYG editors, they also copy the links.

So I am thinking about adding hidden links to my website, inside my content. So they get copied/pasted along with the content. What would be a good way to do it? Any other ideas? Thanks in advance!