Via JoyStiq

" * vertical orientation alone does not scratch DVDs
* horizontal orientation alone does not scratch DVDs
* movement of the Xbox 360 during play scratches DVDs
*
-Movement could be someone running through the house and sending shocks to the system through your floorboards
-Movement is often done on purpose when friends try to show friends the cool way in which the ring of light reorients itself with its fancy mercury switch
-Movement is often accidental, as when annoying controller cables are tripped over in the dark, jarring the Xbox 360
-Sometimes, people just get sick of poorly designed boss fights, and kick their Xbox 360s in frustration
-And sometimes, customers are committing fraud by purposefully destroying games that have been played to completion so that they can be exchanged for store credit that is used to purchase new games"