Engineer,
I have to congratulate you on the way you are handling this, contacting webmasters, etc, before naming and shaming. However, please pay attention to what casinobonusguy has already said… some people, if not a lot of people purchase copy for their sites, and thus it should be the content providers that are named and shamed, and not the webmasters themselves. I know I wouldn’t have the time to vet every piece of content I requested, that’s the whole purpose of hiring copywriters!
I hope you get this resolved sooner rather than later, there seems to be a hell of a lot of content theft going on in this industry, and the sooner we put an end to it the better!