In a recent interview with MTV's Multiplayer blog, Lead Designer for World of Warcraft Jeff Kaplan revealed that eventually players will have a Blizzard Account that will track their achievements across WoW, Starcraft 2, and Diablo 3. WoW points earned through the game's new expansion will be added to the account holder's "Blizzard Level", which will then continue to be raised by achievements earned in other Blizzard titles. “It’s basically a gamerscore,” Kaplan said. “For now the points are just a WoW character score. As we graduate to that Blizzard Account system, which is right on the horizon, it will switch over to a Blizzard Level.”
Taking a nod from Xbox Live's Gamertag Achievements and Gamerscore, Blizzard is capitalizing on the fact that you kids go apes**t over one-upping a nameless, faceless person on the other end of another computer, just so you can brag to your friends and call everyone with a lower score than you a "pathetic n00b". That, of course, means we will all be signing up for this service the moment it becomes available, before begining a non-stop marathon of achievement-whoring. You better bring it.
MTV's Multiplayer Blog: Blizzard Plans To Track Gamer Achievements Across WoW, Starcraft, and Diablo.