I have no objection in principle. Like yourself, I'd have reservations but for the most part I enjoy sharing the experience and getting to try instruments that I may never actually own for myself. At the double bass bash yesterday for instance, I got to try some proper bass fiddles (sorry Owen, heeheehee). Of course, a level of competence is expected at a bass bash but from what you've said you wouldn't be expecting to give the great unwashed in general a go.