I think it's silly that both of the North American GDC's are on the West Coast.
On that, I never understood why more events weren't held in Chicago. It seems like the ideal location for anything going on in North America considering it's in the middle (of the united territories of the US and Canada) and every major European airport flies directly into O'Hare.
Depends on the distribution of developers. I'm sure there are plenty out East, but I only know of DICE.
Besides, it probably has something with GDC being started in Chris Crawford's living room.