I agree in principle, CM, but in reality you sometimes find yourself, as Paulo did, visual with an aircraft whose intentions are unclear, especially if people have differing views as to what "downwind" means (I know that they shouldn't, but they do). I agree that our primary job is to look out and to manouevre as nececessary to remain safe, but the radio, used in moderation, can help. As pointed out above, pilots can sometimes effectively "manage" a busy non ATC circuit through good airmanship and calls.