Minecraft wiki entry for Things_not_to_do, associated text: Looting increases the number of items that mobs drop and increases the chance of rare drops. If the player is using commands, they can get a sword with a high-level looting enchantment that is not usually possible in the game. The player should not use such a weapon to kill a bunch of mobs, as the killed mobs could drop enough items to lag the game, possibly to the extent of crashing the game as well.