Comment 21 for bug 575015

More info on display selection behaviour:

Active displays and layout with the following sequential actions:

Laptop undocked, lid open: Laptop display, single screen
Docked, open: Laptop display, single screen
Docked, closed: 2 external displays, clone
Docked, open: 2 external displays, extended desktop
Docked, closed: Laptop displays, single screen (assumed config as not visible :) )
Docked, open: 2 external displays, clone
Docked, closed: 2 external displays, extended desktop

It looks like every time a lid action is received, the display config cycles to the next of 3 configs (which is pretty useless)