Plagiarizing is a known issues in the fanfiction world. I was speaking to a few other Tweeters who battled a known plagiarist. Our group was created as an early warning/verifying system to help combat this problem. The primary focus of this group is to validate respectable Fan Fiction blogs, bloggers & verify known, respectable authors. This group gives some security to the fans who should know the story they're reading really does belong to the person writing it.
A Google group has been started: http://groups.google.com/group/thefanficadvocate With this group we would hope to have known authors/blogs join. That way there can be a mass emailing system set up when and if there is a story that has been stolen. There by notifying the authors and their readers of a stolen story quickly and efficiently by email.
Twitter Account: @FF_Advocate so authors and readers can have a one tweet notification set up to help take down the purloined story.