One of the first things I took note of while reading the World of WarCraft book was the article about Ninja Players. In the World of WarCraft, we players join raids, instances or dungeons in order to build up on the guild's play as a team and at the same time, to enhance each character on the team. From Armory, weaponry, making achievements and simply for the fun of it. Part of the whole process is to (NEED) if the player badly needs the weapon or armor being dropped within the whole game. (GREED) if the player doesn't need it, and for this matter, if it totally doesn't apply to his character. When on GREED, you give the player in NEED the chance to be able to get the weapon or armor being dropped.
Now, there are circumstances when a guild may lack team players, and will come to a point when another player must join from a different source, this is when Ninja Looters comes in. On my personal opinion, I would say that Ninja Looting is a form of stealing and cheating.
As defined on W0WWiki: A ninja looter is a player who takes loot to which he or she is not entitled.
Some do this in order to get armory and weapons for their Alts or alternate, a secondary character. The rest loot for Gold- generating purposes. They sell whatever stuff they could get in an instance.
Early today, I was victimized by a Ninja Looter who was a Healer we got outside the guild. At first, everything was going smoothly, but as we approach the last level, I noticed that he wasn't doing his job anymore. He wasn't healing our characters. After which, a weapon was dropped, (which everyone else knows I NEED), this player clicked NEED for it, after getting it he left immediately. What a total jerk!
Loots per se was never an issue or even considered as a problem within our Guild, we practice courtesy and respect for each player. Ninja looters, with the attitude and unethical ways you're portraying, it only reflects the kind of person you are in real life. This may just be a mere game for you, but it can greatly show your true color. How hard is it to ask: "hey guys, can I NEED on this?" Our guild is not compose of dumb players and we're not selfish too.