Link: http://blogs.technet.com/markrussinovich/archive/2005/10/31/sony-rootkits-and-digital-rights-management-gone-too-far.aspx

This article by a Windows expert from 2005 explains in some detail how Sony's attempt to include Digital Rights Management (DRM) on a CD release led them to implement a solution that installed a rootkit on Windows, compromising the safety and integrity of the operating system.
I remember in the mid-80's when software manufacturers attempted to implement DRM on their products, it was a failure, mainly because every single DRM solution was broken, in some cases very quickly. Many software vendors spent millions of dollars on copy-prevention solutions, but most of the money was wasted. Eventually manufacturers abandoned copy-protection for all but the most unregulated marketplaces. The music industry appeared to be unwilling to learn anything from the software industry, so we have been treated to ludicrous, ineffective and dangerous solutions like the one detailed above.