This topic is not meant as an attack on Microsoft, it's purely informative in nature. I haven't heard any news that Microsoft ever admitted some XBox 360s being able to leave scratchmarks on disks even when they are properly used. However it seems Microsoft in The Netherlands admitted this can happen to a consumer program on Dutch television. Here's the link to the article, it's in Dutch though:
http://kassa.vara.nl/portal?_scr=kassa_artikel&number=3227123
If this really is the first case anyone within Microsoft admitted this problem is real, it will be harder for them to deny the problem in other areas of the world. If this is completely old news and they already admitted the problem in other places then just ignore this post. Anyway, I just wanted to post this information in case someone found it useful, since not to many people here will follow Dutch news.
