In the run-up (sorry) to today's Boston Marathon, Lou Falcone has been surprised to find that a number of people don't know that a marathon is not just a long footrace but a specific length, 26 miles and change. He's been congratulated on finishing a "marathon" when it was a half-marathon or less, he says, and friends have been asked, "How long was your marathon?"
He wonders: "Has the throwing around of the word 'marathon' in such ways as 'marathon session of Congress' or 'marathon game between the Red Sox-Yankees' so confused everybody that they no longer know what length a marathon really is?"
I too am surprised that anyone living near Boston -- where the marathon is literally a traffic-stopping event -- could remain impervious to the fact that a marathon comes in one size only. But I don't think we should rush to blame such ignorance on the non-literal uses of marathon.
True, the marathon is named for the Greek town from which, according to legend, Pheidippides made his heroic run to Athens. But marathon wasn't applied to the race until the first modern marathon, in 1896, says the OED. And almost immediately, the word was also used for any "long-distance race, competition, or event calling for endurance, esp. one undertaken in order to raise money or publicize a cause": a 1908 citation records "The Murphy Marathon," a potato-peeling contest. And by 1915, a marathon might be any taxing and (subjectively) lengthy endeavor.
Since marathon had acquired its extended meanings even before the race's length was formally standardized in the 1920s, it's not really fair to accuse people of "throwing around" the word, as if its looser senses were modern corruptions instead of standard-issue metaphors. And I'm not even convinced that the non-technical senses of marathon have any connection with people's ignorance of the race's measure. Isn't it more likely that they just don't care enough about the sport to have noticed?