I was thinking about achievments and having a gamerscore today, and i realised what a stroke of brilliance it was by Microsoft!
1. It encourages people to play longer: the more use you get out of one console, the less likely you are to buy another.
2. It encourages people to buy more games: In order to increase your gamerscore you need to either buy or rent, and complete the achiements in more games. This could even be part of the reason that the 360 is such a software beast, it would also increase the favour of MS with rental places like blockbuster (how many people rented avatar for the gamerscore?)
3. It will make people more likely to by the next MS console: This is perhaps the most beneficial of the three, having a gamerscore that exists across consoles will foster a product loyalty to Xbox, and gamers who want to keep/increase their score will more than likely buy a 720 to do so.
This all assumes that the player is interested in their achievments and scores, but as far as ive seen quite a few of them are.
