xpose
These aren't actual ways to stop content theft, more like ways to find out that it's already been done.
I was hoping it would delve a little deeper like to detect user agents of people using cURL and things like that.
The truth is that you can't stop content theft from a technical side unless you ban their IP.
http://simplehtmldom.sourceforge.net/ is a powerful tool to scrape content.
Sean has been talking about an update since December. Don't hold your breath.


Story: How to Put the Kibosh on Content Scrapers & Thieves