When's the last time you heard people in LFR throw around personal insults like "give me that token. your dps sucks ass, you don't deserve it"? Or turn into a bitchfest over people needing and winning loot when they had the heroic versions of the item equipped. I remember I had a DS boss attempt once where we wiped 10 seconds in because none of the healers were healing. They were too busy bitching at the healer who put up really poor numbers but had won some healing item off the previous boss.
The last time I've seen that happen was LFR right before patch 5.0. The new loot system has made LFR 100x better.