Fair use is an affirmative defense to copyright violation. In this case, fair use _probably_ applies. First, it's a transformative use, albeit not a typical on

Fair use is an affirmative defense to copyright violation. In this case, fair use _probably_ applies. First, it's a transformative use, albeit not a typical one. Secondly, TurnItIn's service does not diminish the market for the original work. Institutions pay TurnItIn to detect plagiarism, not to read content of websites it scrapes. Arguably, maybe this reduces the demand from university libraries to buy the works, but since there's still value to have the documents in the library for student access, I'd want some convincing evidence that this is actually happening. Combined, TurnItIn is offering a service that individual copyright holders are likely uninterested in providing themselves, the use does not reduce the marketability of the copyrighted work, and there is probably not a market for this service that individual copyright holders could monetize. This is a pretty good case for fair use.