Isn't this just a fancy derivative of "fill this form out and we'll send you a free iPod?". Because that's all it is..
If you tell me people want achievements, well.. Achievements in games feel good because there's actual skill involved, and it feels like you mastered something. You can't say the same for doing random tasks online. You can't just throw a word like 'achievement' or 'score' on top of what you're doing, and think the effect will be the same.