A large person is not required to wait for all the small people to exit the airplane before exiting himself in an emergency.

A passenger in an exit row is not required to whip the removable window panel out of the opening so fast that he crushes his fingers between the panel panel and the fuselage opening. In some cases the window panel is supposed to be dropped into the next seat row rather than outside where it could fall onto and damage the inflatable raft

Travel tips:
http://members.aol.com/ajaynejr/travel.htm

An airline may do well to notice if some passengers are too large to fit through certain exits. Long range planning would include seating those passengers where their "nearest" exit is a large exit.