Do items get their attributes when mobs spawn, when they die, or when they are identified? If items' attributes are determined when they are identified, will taking gear with better magic find affect item attribute determination?
Items get their attributes when they drop. Otherwise, players could just equip a bunch of +magic find gear, reload the game, and still benefit from the magic find. Rare and legendary also roll their stats when dropped, not when identified, to prevent similar exploiting of the magic find system.
This is also why a common strategy is to equip magic find gear before opening a chest or just before killing an elite or champion monster.