To compensate the playback problems with PC drives, the discs contain copy-protected WMA versions of the tracks that can't be transferred to portable audio players or to other PCs.
The fight is impossible to win from consumer point of view: if the sales increase after the copy-protected CDs are being introduced, labels can claim that copy-protection works. If the sales drop, they can blame ever-increasing P2P piracy and justify adding copy-protection mechanisms to more and more CDs. Arista's artists include Pink and Santana.
Some hardware manufacturers, most notably Apple have taken a very aggressive attitude against the copy-protection mechanisms, since the copy-protected CDs actually are CDs with severe read errors on the discs that PCs can't cope with, but normal CD players can. Apple has announced that playing copy-protected CDs with Macs will void warranty.
Source: CNet