At least based upon the one example of the Groton Road Race...
There were 15 Davids in the race, of which I came in 3rd. So I beat 12 and two beat me, giving a ratio of 12/2, which reduces to 6. Of the non-David men, I beat 167 and lost to 48, giving a ratio of only 3.5.
I would have to do a lot more research to find out first: Is this just a fluke and if I looked at other races this pattern would go away. (My guess is that it is not a fluke--15 is a pretty good number to work with in terms of statistics like this) And second, if it is not a fluke my working hypothesis would be that David is a name which was more popular long-enough ago that the participants as a whole are younger than the average David's age.
Now that I have looked at the data some more, I don't think the age hypothesis holds-up. At first it looked as if the idea was good: All of the Davids are aged between 36 and 60--which seems like the members are not so much old as lacking in any young members of the David club. The slowest five are: 54, 37, 50, 39 and 36; while the fastest five are 42, 45, 45, 39, and 60.
What really made me discount the age hypothesis was that my assumption about the relationship between age and speed is incorrect. I figured younger=faster, but look at this:
48 men in their 30's ran with a median time of 52:06
97 men in their 40's ran with a median time of 48:50
37 men in their 50's ran with a median time of 51:50
*there were only 11 men in their 20's so this didn't seem representative and I didn't include them in this analysis.
The men in their 40's were by far the fastest and largest group, even the men in their 50's were faster than the 30's guys. There were 5 Davids in their 30's--they were the ones dragging down the Davids.
Update: We were a platoon of Davids, not An Army of Davids that's something else.