The Mazel Bomb (or adj. Mazel Bombing) is the fine art of getting a bunch of friends on Facebook to wish a Jewish, mutual friend a hearty Mazel Tov despite there being no reason. The result is that with enough people involved in the plot, the wishes will be seen by many others who will join in despite no knowing what is being celebrated. The result is much laughter and confusion all around.
Friend 1 to Friends 2 & 3 : "I've hidden this message from Victim. Lets all Mazel Bomb him and let the hilarity and confusion ensue!"