How many is too many?
Heh. I'll play this game.
I seem to remember from some WotC demographic info that there are 1.5 million people who play D&D once a month (and another 1 million that play some type of RPG at least once a month).
So, given that, and factoring in the other places/people/things that the open call was sent to...
I'm gonna guess that the get 37,923 submissions.