I wrote a post some time ago about how it is difficult to find and control plagiarism for publishers. The recent case of Harvard sophomore Kaavya Viswanathan (story here) makes it even more important to nip this kind of ‘inspired’ writing in the bud.
So why isnt this idea a good one? Convert the text to electronic form (i bet the author has the original in electronic form) and run a comparitive search using a database of a huge collection of books (Google has one). I am not saying its foolproof, but it sure is a step towards discouraging plagiarism, conscious or unconscious.