I have ninjaed often in 5man end boss because at that point group cannot kick me (or even if they could it would be pointless because dungeon is already over). I do that only for loot, very rarely to steal from my group members (exception when they have been dick). I don't like position where I have choice between 10g/ethereal shard or my fellow wow player feelings. However I often take money because I feel bad throwing money away.
Recently though I had discussion about this with other player. He mentioned that if he has worked towards something, he doesn't like rewards to be stolen. That made me really think more about the position of one whose loot I ninja, and feel bad. Also ninjaing tarnishes your reputation.
(My personal story)
I was in my realm+faction best raiding guild as social for 16 months, I chatted much, really liked people there and I felt like they liked me too. However on one night we happened to talk about incoming 5.2 patch. I told that I have been preparing our small realm+faction for it by funneling enchanting mats here, added by JK I would do it anyways. Apparently officers however didn't like it, as next day when I log in I find myself guildless. I talked about one of them, (he's the "other player" mentioned above) apparently that stuff gives bad reputation to guild. (though while being in small realm+faction 99% of people who I meet in LFG are from somewhere else, so what's the big deal? IMO) and he didn't see anything good in having people with so loose morale around him.
What is your stance on ninja looting in LFG and thought process behind that stance? And what do you think about ninja looters?