AVOID: Alliance side Warrior Stevefox
He wasn't exactly ninjaing, but more of being a total asshole to group members. Near the end of a Gnomeregan run, we have a DC, and we pick up a druid friend of the mage. As we are about to pull the final boss, he kicks the guy we just picked up, and reinvites the guy that DCd (this was about a 25 minute time difference mind you, as the new player had to fly to IF, and run to Gnomeregan). Obviously we are disgruntled about that, and just replies with basic bullshit like "QQ", and as we are killing the boss, kicks the mage from the party (who was guy that invited the new druid) preventing him from getting loot, and preventing him from getting progress on his quest to kill the final boss.
Unfortunately I was unable to get a screenshot of the mage getting kicked before the boss died, since I DCed before I could screenshot it.