I was watching the Warhammer Online video podcast on quests again, and the description of WAR's "kill collectors" quests made me think. Paul Barnett is a funny guy, and spins a great yarn about how it is better if the quest giver rewards you for kills that you already did in the past, instead of sending you out to kill bears when you just spent an hour doing so. You don't even have to keep the bear paws in your inventory, you just get a reward because the game remembers you killed stuff. But is that really better? Or is it totally against the purpose of quests?
Paul says something along the lines of "so if you are wandering along somewhere and see a lot of monsters, and you are not too sure whether you should bother harvesting them, remember, somebody somewhere wants them dead". I'd call that reverse questing, first doing the quest and then looking for the quest giver. One minor problem I have with that is that it isn't very logical from a story point of view. I can't see the hero going into a village and shouting on the marketplace: "I killed 12 orcs, 8 bears, and 17 wolves. Who wants to reward me for that?". Because even if somebody in the village wanted those orcs or wolves dead, he wouldn't be giving out rewards after the fact, unless he had made a deal with the hero before to kill those orcs.
But the bigger problem is from the gameplay point of view. It means you are back to guesswork about what you are supposed to do. You see some monsters and you just randomly kill a couple of them, hoping there will be a reward. You don't know whether there really is a reward, where to get it, and how many mobs you are supposed to kill. There is no real purpose behind your actions, except for some bonus reward on top of the xp and loot you get for the killing itself. Rewards aren't the purpose of quests. If you just wanted to give out a bonus award for killing 30 wolves, you could do it like Lord of the Rings Online, which on killing the first wolf automatically puts the "kill 30 wolves" goal into your deeds log, telling you that you'll receive a title for killing 30 wolves (and a trait for killing another 60 one). You wouldn't need quest givers for that.
The purpose of quests is to guide you, to direct you into areas where you otherwise might not have gone. If you are new to some area you simply can't know whether you should go north or south to find mobs of your level. Go the wrong way and you could either get eaten by monsters far too strong for you, or bored by mobs that are far too low. But if you open your quest journal, you'll find a quest color coded to show that it's for your level, and telling you to go north to kill 10 wolves. That gives you a goal, a direction to go, a hint what you are supposed to do next. World of Warcraft did this especially well, up to the point of detecting that you were a bit too high for this area and giving you a quest to go to the next one. The purpose of quests is to be your guiding angel through an open world, where you don't have the linear storyline of a single-player RPG. Or as the WAR podcast says, quests are the story of a MMORPG. Somebody handing you a bag of gold because you killed some wolves Tuesday of last week isn't much of a storyline, in my opinion. Fortunately WAR has a lot of other types of quests, I assume that the others give you more of a sense of purpose than just rewards for random killing.