Sony is testing the waters with a new "must register game" system.
On the latest PSP title: "SOCOM: US Navy Seals Fireteam Bravo 3" released a few days ago, you will find it has the famous DRM which normally is used only before on PC based games, now it finally hits the console world.
Anyone that purchases this game from a store, will need to register the title thru the PSN store before they can connect online with it. Those that download it digitally, the PSN will auto-register it. But those unlucky folks to pick it up cheap used, will have to paid Sony $20 for a new "entitlement voucher".
You can read the full interview with Sony on why the changes and possible PS3 usage of DRM system over at IGN: