From [URL=http://arstechnica.com/]arstechnica.com[/URL]:

[QUOTE]Borderlands was a highly anticipated release on the PC, but a one-week delay of the PC launch meant that console gamers were able to enjoy the gun-collecting goodness ahead of their PC gaming brethren. A few gamers were lucky enough to find stores that were willing to sell the boxed PC copy of the game before the street date, however, but when they installed the game and tried to play, they found that without the title being authenticated online, the disc and key were worthless.

The problem? They forgot that buying a PC game doesn't involve a product, but a license.[/QUOTE]

Full article can be found [URL=http://arstechnica.com/gaming/news/2009/10/games-you-cant-play-the-early-copies-of-borderlands.ars]here[/URL].