I've been playing MMO for 13 years now... And what i call Ninja Looting is people rolling "need" on every loot.
Rolling "Greed" on item you don't need for you char, you just want it either for your companion or for making money it's normal and it's for that purpose that "Greed" was made.
Saying "You're Ninja Looting" to peoples who only roll "Need" on what they need it and "Greed" on what they don't need it, it's just plain stupid (sorry, but it's what i think) because "Need" > "Greed"... So people rolling "Need" don't have to worry about losing their roll to someone rolling "Greed".