Lithium battery fires are terrifying, there was one in January on the Toronto subway. Thank goodness they were able to evacuate everyone before it exploded, one of my classmates was on a different car when it happened and he said he heard the explosion as he was leaving the area.
I also learned that people apparently packed their laptops/iPads/portable consoles in their checked baggage, and I've never had peace of mind on a flight since that day.