I find my content all over the net, sometimes credited and sometimes not. There is not much you can do if you publish your feeds. I have heard of a WordPress plugin for adding copyright information to your feed.
Week in review: Rights and wrongs on copyright | CNET News.com
Meanwhile, many bloggers feel they are being ripped off by automated digital plagiarism, in which software bots copy thousands of blog posts per hour and publish them verbatim onto Web sites on which contextual ads next to them can generate money for the site owner. (read complete article).
How big a problem is plagiarism to you and your website or blog? What security measures do you take to protect your images, content and design? Do you have an horror stories to relate?