Personally speaking, unless a player has specifically engaged in action that will drawn aggro (looking back in time at a Tindalosian, etc.) as a Storyteller I try to portion out misery in a fair manner. As a more fair approach, when something bad is about to happen when I run Call of Cthulhu, I assign each player a number and then roll a die in plain view of everyone to determine who the lucky winner is. That way, when an eldritch monster tramples a player character flat and then devours the flattened remains whole, the Storyteller avoids the appearance of bias.