What do Undead Knights, Naruto Shippuden: Legends: Akatsuki Rising, NBA 2K10, Star Wars: The Clone Wars: Republic Heroes and Cars: Race O Rama have in common? All of these are PSP games released on UMD after the PSP Go's October 1 launch -- and all are currently without a digital equivalent. Owners of the Go system are unable to play these games because they simply aren't available on the PlayStation Store.

Once again, Sony's hands-off approach to the PlayStation Network means third parties are responsible for getting their content on both UMD and the PlayStation Store. "It's up to individual third parties to decide if and when to publish their UMD releases on PSN. Most, if not all, are on board, as this is a revenue opportunity for them," we were told by Eric Lempel, SCEA's director of PlayStation Network operations. Namco, the one publisher that returned our request for comment, noted specifically that "there are currently no plans to release Akatsuki Rising on PSN right now," despite its October 6 release on UMD.

We highly encourage Sony to make simultaneous digital releases of PSP games a requirement for publishers, not merely a suggestion. The company previously issued a mandate for PS3 games to include trophies in 2009 -- a similar policy must be enforced on the PSP. Without it, there's no guarantee that all future PSP games will ever be playable on the PSP Go.

This article was originally published on Joystiq.