Master Loot is a good safeguard against ninjas when a guild or group includes characters they have never partied with before. With one trustworthy person being the only one to loot a boss's body and distribute the loot there is no chance of a ninja looting the body or selecting need or greed after everyone else has passed for rolling.
However, some players are against using the Master Looter rules, possibly due to time issues, or because there is the risk of the Master Looter himself/herself being a ninja looter (which this loot system is meant to prevent).
How to distribute loot as the Master Looter
When the Master Looter (who is the Party Leader in a group of five, but can be assigned to someone else by a Raid Leader in a Raid), loots the body, the loot window comes up just like when playing solo. When the loot is clicked a submenu appears off to the side of that particular piece of loot listing every group in the raid. Each of those groups lists the people in that group when moused over. The Master Looter then clicks on the specific name of the character getting that piece of loot. When the Master Looter assigns a Bind on Pickup piece of loot, they also get an alert verifying that the loot is definitely supposed to go to that person.
Any loot on a dead mob can only be looted by the player who was Master Looter at the time that mob was killed. If the Master Looter leaves the party, no one else will be able to loot that mob.