At the New York City unveiling of the system, Cerny talked about PlayGo, the system by which the console will download digital titles even as they're being played.
"The concept is you download just a portion of the overall data and start your play session, and you continue your play session as the rest downloads in the background," he explained to Gamasutra.
However, PlayGo "is two separate linked systems," Cerny said. The other is to do with the Blu-ray drive -- to help with the fact that it is, essentially, a bit slow for next-gen games.
"So, what we do as the game accesses the Blu-ray disc, is we take any data that was accessed and we put it on the hard drive. And if then if there is idle time, we go ahead and copy the remaining data to the hard drive. And what that means is after an hour or two, the game is on the hard drive, and you have access, you have dramatically quicker loading... And you have the ability to do some truly high-speed streaming." http://www.gamasutra.com/view/featur...rk_.php?page=3
And he didn't say anything about the data only being temporary. We definitely need more clarification on this.