It looks like I may have spoken too soon in my article on the Mac being immune to the Sony Rootkit—Advantage Macintosh.
On Macintouch Darren Dittrich reports that Sony's DRM software targets Macs too. Digging into the "enhanced" content on the disk, he found a Start.app that, when run, shows a license agreement, then asks you for an admin password. On entering this, it installs two kernel extensions, PhoenixNub1.kext and PhoenixNub12.kext.
Note that these aren't the rootkits that infect Windows PCs -- Sony's Mac crippleware comes from a different vendor called Sunncomm.
Dittrich reveals that the Sony EULA that he agreed to indicates that they will be installing software, so read those agreements and question anything asking you to login as an admin. Caveat emptor.
The good news is that this is apparently not the same technology used in the recent Windows rootkits (made by XCP), but rather a Mac-aware DRM codebase developed by SunnComm. And the second main difference between the Windows and Mac versions of Sony's Spyware is that it doesn't automatically install on Mac OS X.
I also reported on the PowerPage that Copy Control discs carry their own Mac OS 9 player, so watch out for that too. Keep an eye out for CDs that use the Copy Control trojan and avoid them like the plague. (Thanks Boing Boing)