While there are several reasons to be bullish on Cliffs Natural Resources (CLF -1.54%), these must be weighed against the cautionary tales that tell its story. For Cliffs in particular its reliance on steel and a few major customers for the bulk of its revenue places it in a precarious situation. Due to steel's long life, global growth is the ultimate driver behind Cliffs' success, and the loss of any one of its top customers could significantly impact its stock price. Take a look at this quick video from Motley Fool energy and materials analyst Taylor Muckerman for a little bit more color on these issues and more.