There are plenty of reasons for WoW addicts to keep coming back for more. There are always new raids to run and better loots to acquire. However rumor has it that Blizzard may be implementing something else to help distract you from the real world. Achievements.
Yes, we've all seen achievements on our Xbox 360s among other places, so they're nothing new to the gaming community. I've always been a little torn on the subject of achievements. Sure, I get a warm fuzzy feeling inside when I complete something, but after a while trying to unlock them all starts feeling more like work and less like fun.
I'm not really sure that this is something WoW really needs. Honestly there are going to be a lot of low-level achievements, or ones that will take a long time to accomplish (such as the 2,000 quest one depicted above) that longtime veterans really aren't going to feel like completing. I seriously doubt that they'll go back and give you achievements for things you've already done in-game.