But think of the singer/guitarists (like me!) who aren't very good guitarists. It's bloody hard enough singing and playing at the same time, without doing it in a different key, one that you're not practised with. ;-)

I appreciate that, for a performer of competence, it can be hard to listen to a parade of lesser talents, as happens when the compere is presiding over 'singing round,' but maybe this thread will lead to some of us rethinking our 'keys.'