Achievements are undoubtedly the most interesting concept to come out of this generation of gaming, and has now not only spread to other consoles, but computer gaming and even computer sites (this one) BASED on gaming.  On the surface they seem quite pointless, something my friends like to remind me of, but there is something incredibly gratifying about receiving that "Achievement Unlocked" landmark.  They often include some of the most menial tasks, asking you to do things that without achievements most gamers would never even consider bothering to think about, even if offered arguably more tangible rewards like special modes or new costumes. Now don't get me wrong, i'm just on the tail end of obsessive compulsive achievement collectors, I will rarely scrape the bottom of the collective game barrel in search of more achievements, but I still find myself doing things in games that I would never do in an effort to get an extra few gamer score out of my games.  I suppose it's just the visible confirmation of what you've accomplished, the time you invested, that makes achievements desirable to gamers like myself, and I think a concept that can be applied to human nature in general. 
 
James Schell touches on this in an interview for a recent issue of Game Informer.  He predicts an eventual complete integration of video game style achievement tracking into every day life. You read the newest Twilight book, and receive an achievement (Hopefully saying something like "Seriously??"), run a 5k, receive an achievement. People are constantly looking for recognition for what they've done, even if other people don't care, just seeing it validates our "Achievements".