I often see status updates on Facebook where people talk about how Karma finally caught up to their enemy.
What people don't seem to understand about Karma is that when you rejoice in someone finally "getting theirs" you've just screwed yourself. Karma will then come back to get YOU for your vengeful feelings.
So even if you feel like Karma balanced the scales of justice, don't celebrate the misfortune of others even if you feel they deserve it, or you'll just tip the scales out of your own favor. Negative energy never benefits anyone.