Whether authentication and other DRM methods work or not, game developers often insist on adding layers of anti-piracy security to their titles. Ironically, it's usually the legitimate buyers who get the most frustration (pirated versions just edit out the security altogether); it's even more frustrating, though, when you're asked for CD key that hasn't even been supplied. That's what has been happening to some NBA 2K9 owners.
Faced with a prompt to enter a CD key in order to install the PC version of the game, it's then pretty annoying to search through the packaging only to discover that no licence code has actually been supplied. Several gamers are reporting similar issues, unable to play while those with pirated versions are busy slam-dunking.
Valve are now using Steam to circumvent the issue, with buyers able to install NBA 2K9 as long as the CD is in the drive. However it does presume that the computer they are playing on has internet access.