One of the many things that make me sigh forlornly (right up there with how goat's cheese is always the token vegetarian option at those many restaurants who just don't give a crap about me and my herbivore brethren, Nazis and fashionable haircuts) is achievement systems in games. Not the essential concept (a pat on the back for doing something awesome makes perfect sense), but what it can become - something that can overwhelm the game itself. I hear dark tales of people who buy/rent mediocre 360 games purely because they're known to contain easy/excessive Gamerpoints. It's not a surprise that World of Warcraft is, reportedly, soon to introduce achievements of its own - there's arguably no game better suited to them - but I do wish the bloody things would stop popping up everywhere.
I entirely understand their appeal - it's just chasing the place at the top of the high score table, as gamingkind at large has done for decades, but, personally, an arbitrary reward for following a pre-determined set of rules seems very much at odds with what I most love about videogaming: having unique, personal experiences. My favourite moments during my two or so years with World of Warcraft were those that only mad accident and random exploration could have brought about, so reports that Wrath of the Lich King will include an achievement system has me worried the scope for ultra-adventures are that much more reduced in favour of chasing yet more statistics.
That said, it's very much the obvious thing for the game to do (the likes of LOTRO and City of Heroes are already doing it) and there's a reasonable chance that having a specific, wider goal will increase the sense of purpose during those times when finishing yet another quest or increasing your tailor skill starts to feel a little grindy and futile.