I think this same line of logic is why Achievements and Trophies work on so many levels. I honestly believe those little bonuses have driven the game sales more than some people like to admit. It's the added benefit of leveling up in two places, in the game you are playing, and among your friends on the XBL or PSN leader boards. Each time you reset your COD game, you can promise people that not only will they get to level up with all their friends again, they will also get another 1000 XBL gamer points, or another Platinum trophy.
I personally think all of this stuff detracts from the gaming experience as a whole. It turns the simple fun of playing a game into more of a job, one where you have to work to get better at the same thing over and over again in order to get that elusive rank or achievement.
It seems to me that the game companies realize they've created an addictive and competitive environment. Innovation isn't as important as designing the perfect drug, if you will.
Nice article.