I have had quite a few take home exams, mostly because they required you to be online and were a lot longer than 2 hour exams.
When taking these exams and answering questions (all essay questions) I've typed in the question into Google and bam. I find the same questions used from some PDF associated with, often, a different university and the PDF has either the answer or guidelines as to whether or not the student gave a close enough answer.
This has happened in 3 courses so far and I brought it up to a professor a year ago and she had no idea that the PDF she got test questions for had the answers on the same PDF online.
I assume it isn't students putting these PDF's up because the PDF's often have more questions than are on the exam and will have pages with a university name, class, and symbol which are not given on the exams handed out.
So, why would a university use questions from another university when a simple copy and paste reveals the answers or at least guides as to how to answer?