Firstly it seems Microsoft has now classed the Sony BMG rootkit as malware and future versions of it's security software will remove it.

We have analyzed this software, and have determined that in order to help protect our customers we will add a detection and removal signature for the rootkit component of the XCP software to the Windows AntiSpyware beta

Secondly, this article on the Electronic Frontier Foundation is a more than interesting read. They examine the EULA on Sony's cd's and come up with some very worrying conclusions. Thanks Hard|OCP

Sony-BMG can install and use backdoors in the copy protection software or media player to "enforce their rights" against you, at any time, without notice. And Sony-BMG disclaims any liability if this "self help" crashes your computer, exposes you to security risks, or any other harm.

Yet more Sony shooting themselves in the foot to be honest.