We have experienced difficulties with certain aspects of http://netnam.reykjavik.is lately.
One of the questions that comes to my mind when analysing the dilemma: what happens if somebody with the system role of manager or system administrator steps in as a teacher? Is it advisable, to begin with?
This person will have easier access to questions in question banks outside the course context.
If a course containing quizzes with questions from question banks in other contexts is exported?
Is it possible at all? Moodle complains, at any rate!