You can't really protect yourself completely I don't htink, which is a shame. The only way around it is to keep hammering home the importance of original content, and one day, maybe, people will pay attention, and then nobody will want to copy any content! fingers crossed...
Why not contact them and tell them for using the content, get a one way backlink from them to your site and it must state your name/company and what-not. Free advertising for your services....