Too Lazy To Game?

Quite some time back Endie and I were talking about the fact that many people would take their XBox 360 gamer score very seriously and that the difficulty in unlocking achievements would be a factor in a game's purchase. It seems that someone is now offering a service to gain achievement points. I can't really understand why I'd want to. Surely part of the point about getting achievements is that you've achieved it? Also presumably this means you have to hand them your XBox Live details so they can log in as you (also do you get to chose the games you unlock or will you suddenly become a Fifa fiend).