This one by far takes the cake, and I can't even begin to fathom the logic that goes into it; especially from tanks and healers without whom a dungeon cannot be completed. WoW had a similar problem at one point with people entering BGs like Alterac Valley (a 40 v 40 pvp scenario notorious back in the day for lasting hours, even days) and either going afk or just fishing and not engaging in the battle. The problem was fixed by adding in a "Report AFK" option under player names, and then, if I remember correctly, a system that just auto booted you from a BG if your character ever became flagged as afk.