Below is a quote from an article on Sony's new DRM (Digital Rights Management) technology. Basically, DRM is a way for Sony to protect their content from piracy.
You buy a CD. You put the CD into your PC in order to enjoy your music. Sony grabs this opportunity to sneak into your house like a virus and set up camp, and it leaves the backdoor open so that Sony or any other enterprising intruder can follow and have the run of the place. If you try to kick Sony out, it trashes the place. And what does this software do once it's on your PC? Well, here is (via David Berlind's excellent breakdown of the issue) what Amazon's CD listing page has to say on the subject:
"This product limits your ability to make multiple digital copies of its content, and you will not be able to play this disc or make copies onto devices not listed as compatible. Content/copy protected CDs should allow limited burning, as well as ripping into secure Windows Media Audio formats for playback with most compatible media players and portable devices. In rare cases, these CDs may not be compatible with computer CD-ROM players, DVD players, game consoles, or car CD stereos, and often are not transferable to other formats like MP3." By Molly Wood
Read the rest of the article here.