Going through my referal logs earlier, I noticed a highly unusual domain. I followed the link and it came from a report on a page with the following text: "Plagiarism Prevention Recognized worldwide as the standard in online plagiarism prevention, Turnitin helps educators and students take full advantage of the internet's educational potential." Moral is learn how to paraphrase...
Turnitin is a bandwidth hogging bot that scans your sites to add to their own DB but it is never used for a public search-- only their profitability. The bot doesn't have much in the way of bandwidth manners.. I block it.