The "Dumbing Down" of Marathons?

Forbes points out that marathoners are slowing down — dramatically.

"In New York, which along with Boston hosts the nation's most prestigious long-distance race, the median male runner in 1983 ran the distance in 3:41:49, an 8:27 minute-per-mile pace. Ten years later the median time was 4:14:27, or 9:43 per mile. Last year, the median runner had slowed to 4:28:41, or 10:25 per mile."

The fact that Forbes even publishes features about running says something, doesn't it?