ORIGINAL: j.duncker
My old club in the UK would not alow a model to fly with unpinned hinges.
If a club ever told me that I would tell them that I would be happy to hold a seminar on installing hinges as none of them appear to know how to do it.
For the most part, I never pin a hinge, but of course, there's an exception to every rule. If I am uncomfortable with the way a hinge installation went, then I will use the added insurance of pinning them. This has happened two or three times in my 50 years of building.