Dan Simmons on drm, Music lovers caught in DRM battle
"The technologies used to stop you copying as you wish are called digital rights management - or DRM.
Most DRM formats now count the number of copies you make and stop you burning when you reach that limit. iTunes is perhaps the least restrictive for this.
The number of times you can copy music to other computers, laptops or portable players is capped in much the same way.
The trouble is that if you upgrade your hardware too many times you may have to buy your music collection all over again.
Copy protection software on some newer CDs makes copying, or "ripping", them to a computer difficult too.
Some send data to your ripping software designed to confuse it. Others simply will not allow you to access the copy command. "