I'm sure we've all had someone dash ahead of us when we're out gathering to take our mining node, our herb, or even our skin. It's frustrating when it's a member of the opposite faction who does this. On a PvP server, you might kill them, on a PvE server, your only recourse is a /rude. It's more annoying when it's a member of your own faction and you can't even kill them. Ultimately the same is also true of Daily Quests and some quest mobs. Whenever recourse's are scarce, bad blood settles in.
I have never seen a quest that brings out the worst in players than "Junk in My Trunk" in Utgarde Pinnacle. For this quest you must gather items laying around the instance. There are not enough for a full group on the quest to pick therm up on the same run, so many people jockey to be the first to get their junk. The first time I ran that instance I was amazed at how greedy people would be. The tank would pull but the healer was off picking up a silver bar or a bauble. You guessed it, wipefest.