Contact the webhost and they do generally take your enquiry seriously. I have heard many cases where they temporarily take down the site as a precaution.
I've been dealing with content thieves for years. They actually scrape your site or your RSS feeds, then make bogus blogs or sites with google ads. I always report them to google in the hopes of getting their asses banned. I also put internal links to my own site so that if they do post my content elsewhere, it links back to my site. One other think I'll do is watermark my images with my URL so if they steal them, I still get some sort of publicity out of it.
I think finally I have to approach this way. Let me see. I'll keep updated on the development on this issue.