You can't stop them, but you can slow them down a bit. Most thieves don't do their homework and don't remove some of them. The deeper in the content you can bury a link, the less likely it will be removed. You can at least back track from referral logs. If you are using examples in your content, talk about your site.
Thieves are far less likely to take the page if it is about the site.
Relate personal experiences in your content. Same as previous. Have a copyright notice visible and in an html comment. If the page is dynamically generated, put their ip address and host in an html comment. Then watch for 404's to that directory.