True, sorry I should have qualified the statement a little bit better but I am thinking that the majority of people would require something on the reasonably small side. You would need a seriously big passive rad to dissipate let's say in the region of 1000w. I would be glad to be proved wrong though
My experience is based on trying to cool an OC 2600k with a D5 and a BIG household rad (1m x 1.5m). It was ok (ish) when the ambient temps were low but once that liquid heated up the temps were not what I would call good. It was superb in the winter tho when it was mounted outside
