This may be an argument against breakfast for the sedentary, but athletes on extended training programs usually need to eat in the morning. You're much more likely to hit the wall on an empty stomach, a few hours into your training.
I'd also add that I am an amateur long-distance runner and just completed a medium distance run after fasting all day and performed fine. Had it been a race, probably less so. But the myths of caloric necessities have been greatly exaggerated.