Guys this is really frustrating, if you are among one of those planning to buy Gran Turismo 5 DLC than hang on, and please keep one thing in mind that its locked to one account.
This means that if you make use of other account on your PS3, you won't be able to access the DLC content. This has irritated fans of the game, and has caused a huge uproar on PS blog.
Gamers are now asking for refund from Sony and Polyphony Digital as it seems like it was intentional from developer. For proof check out the image below.