Was it a mistake? As the global commodity boom disintegrated over the past eight months and the wisdom of decisions made when the going was good has increasingly been called into question, that is something many industry executives have been asking themselves. Some strategic moves made at the height of the bubble, such as Rio Tinto's $38.1-billion acquisition of Alcan, have been proved to be all-but-disastrous for the buyer; others, notably BHP Billiton's aborted bid for Rio, nearly so.

But what about the wisdom of a couple of other raw material acquisitions—Steel Dynamic Inc.'s $1.1-billion purchase of scrap processor OmniSource Corp. and Nucor Corp.'s $1.44-billion buy of...