My Small Business Trends site is a blog and I encourage people to use my content.
All I ask is that they give me credit for it and link to me. I issue RSS feeds to encourage such use -- right now over a dozen sites use my content and I am happy for it. See the Articles section of this site for an example:
http://www.small-business-forum.com/articles/
I freely quote other sites, too, but always link to them and give them credit.
Almost always they are happy with the free PR and "Google juice" I give them. And under copyright law as I understand it (U.S., anyways) quoting a small portion and crediting the copyright owner is considered "fair use" and allowable.
Now if I were using their content without linking or crediting them, then I'm sure it would be a different story. Or if I used up their bandwith by direct linking their images -- well, that's simply dirty!
You might want to think about whether you can turn the content theft around to your advantage for free PR.
Good luck,
Anita