Would feather falling out of a flying creature's space provoke an attack of opportunity?
The scenario: As you are feather falling, a flying creature flies and attacks you; you then are forced to fall out of his combat range.
Attacks of Opportunity are provoked by actions taken in combat. Falling is not an action, it is just what normally happens to your character when you are not supported by a floor.
An enemy that takes certain actions while in a threatened square provokes an attack of opportunity from you.
Casting Feather Fall also does not provoke an Attack of Opportunity because it is a spell cast as an Immediate Action. Immediate Action spells do not provoke Attacks of Opportunity. The Core Rulebook explicitly states Feather Fall as the example of an Immediate Action spell not provoking.
Table 8–2: Actions in Combat [Whether or not they provoke]
Cast feather fall: No