when people feel sad about something that doesn't really affect them, just because the enjoy feeling sad. most of the population do it when someone famous dies. people pretend to know the deceased, or have some connection with them, just so they can enjoy some grief.
Example 1. When JLB Credit goes under in the TV series Peepshow, Jeremy is sad even though he has only been working there for a couple of hours.
Mark: You're free loading on my trauma. You're a grief thief.
Person 1: Why are you wearing black and crying?
Person 2: Didn't you hear? Trevor that we used to go to college with died.
Person 1: What? And? You never even spoke to him in four years of going to college with him, and I seem to recall you thought he was a knob jockey. you have had no contact with him for the last 7 years and his death will have exactly no impact in your life what-so-ever. you're such a grief thief.