As I was perusing the very first review of Grand Theft Auto 4 yesterday, I noted that the "collectibles" in that game are going to be pretty intriguing. While a lot of collectible items in games (say, all the packages in the previous GTA games, or the flags in Assassin's Creed) are fairly superfluous, I find that some (like the orbs in Crackdown and the billboards and jumps in Burnout Paradise) actually make the game more fun -- while traveling through the game world, you can keep an eye out for extra stuff to do and see.
World of Warcraft has never really jumped in on that idea, however. Obviously, there are plenty of collecting quests, but usually they're for killing mobs. And there are plenty of things to collect in the game -- noncombat pets, tabards, and mounts, and so on -- but none of them really give you a reward when you find a certain number of them, or give you bonuses based on how many you've picked up.
Is that a good thing or a bad thing? For me, hiding some fun, optional collectibles (and giving small rewards based on just finding them) in a world as lush as Azeroth would make exploring an already great environment better. But I'm sure some would see it as a cheap tactic to make people hunt for widgets. What do you think?