From: Northwestern Georgia, USA
If I was playing Q-Ball, Miller, John III, Nemo, Chez, Alfred, Chickenboy, Cribtop, rader, or any of another two-score experienced players, I wouldn't defend Noumea. To do so would be to place troops in a place that can't be defended early in the war against an experienced player. (This is a general rule - there may be exceptions, but exceptions that would only apply under very limited circumstances).
If I was playing somebody new to the game, and if I was relatively exprienced, I would definately consider garrisoning Noumea....as long as I really knew what I was doing. Under those circumstances, I could really mess with the game plan of my opponent.
If you have two fairly inexperienced players engaged, a defense of Noumea by the Allied player early in the war may well turn into a meeting engagement. IE, it may turn into a vortex that draws increasing amounts of troops and other assets, with heavy losses by one or both sides. That can be very fun, but it is usually pretty unpredictable as to who will win.
Bottom line though, Noumea is Japan's if Japan wants it, when Japan is led by an experienced player.