.I think your'e wrong, at least with respect to the US. People here will come up with the names of Eric Heiden, Mark Spitz and now Mr. Phelps before they remember ANY 100m medalist. You've already indicated that you would be happy to watch the entire broadcast of a marathon...that makes you extremely atypical with respect to the general population (this is NOT a criticism, just an observation). Most people in the US don't follow track and field, even the 100m, with any regularity or particular interest.
I just did an informal poll of 23 people here in the operating room lounge, none expressed any dissatisfaction with not having seen the 100m final live. The majority didn't see it at all.