BSDB of Concept Questions

I was truly illuminated by Eric Mazur's talk about peer-education. It is a bit long (1h), but worth it if you are wondering about alternative ways to teach your students (or to be taught, if you are a student):
I immediately thought that a database of (good) concept questions would help people to move their course from traditional teaching techniques to this kind of problem based teaching. Eric was quite positive when I talked with him about it, and a few days later admitted to me that the main problems with his current database (http://ilt.seas.harvard.edu, with about 10,000 users right now) was that 1) few people were submitting, and 2) the database contained some "bad" items (e.g. "Test1", and some fact-based questions when they should be based on concepts): those are exactly the problems that boot-strapping databases are trying to solve! Concept questions would be a better material for a prototype of boot-strapping database than the solved problems (for assignments and exams) that I was previously considering, first because the criteria to evaluate them are much more clear and faster to check, and second because there is already a set of items available (the incentive to use the boot-strapping database rather than the database freely acceptable would first be that the former was "cleaned" from garbage question, and later that it would grow bigger than the original free one). Plus, instructors using "Concept Questions" they are by definition open to change their way of teaching, I expect them to be open (and nevertheless critic) to use a better tool to exchange their work. I will post on the basics of the concept of boot-strapping database later, but for now it is time to get down to program some PHP and MySQL!