The Seattle Post-Ingelligencer (it's a newspaper and a website!) has a story up in its Microsoft-focused blog detailing some newly released documents stating that the Xbox 360 manufacturer was aware of issues with the Xbox 360 that would lead to it placing deep, game-destroying scratches onto discs. Specifically, the discs can wobble if the console is moved while the machine is still turned on and rub up against some plastic bits that'll engrave your discs with pretty circles. This happened to me a few times when I had my console up on its side. After losing two games, I wised up and laid it back down. I wasn't even trying to reorient the console when that copy of Prey went down. Honest!
This stuff is all coming to light as part of potential class action lawsuit. Microsoft has since responded and claimed that the issue isn't unique to the Xbox 360. I once dropped a really crappy portable CD player and the disc inside was ruined in nearly the same exact way as the 360 game discs are, so I guess I can vouch for Microsoft's rebuttal, too. Still, the degree of movement to ruin 360 discs always seemed to be really small, like it was the sort of thing that could easily happen by mistake.
In the below clip, the part of my Prey disc is being played by the man in the body cast. The guy in the hat represents the class action lawsuit, and the lady is uh... a lawyer or something. Look, it's been a long time since I've seen Turk 182, OK? Back off.
Also, hey, have you ever ruined any discs by moving the thing that was playing them?