James Beltz is a photographer out of Moore, Oklahoma, who also runs a very informative Photo Tip website. Recently, he took on an issue that is near and dear to his (and all photographer's) hearts...theft of copywright images.
He has put together an informative webiste to help you defend yourself against this type of crime. His site walks you through exactly what to do to protect yourself; and what to do if you're a victim of photo theft.
Good luck and protect yourself!