The initial list of games available as part of Sony's UMD Passport offer suggests that some key publishers have not yet signed up for the service.
The scheme was set up to allow PSP owners intending to upgrade to Vita to preserve their current collection of UMD titles. Those who register their old games with Sony will be able to purchase a discounted digital version for use on Vita.
However, Siliconera reports that the list of titles available for UMD Passport is 262 – that's significantly less than the 606 PSP games currently available for download on the Japanese arm of PSN.
Publishers notable by their absence from the service include Square Enix, Konami, Capcom and Namco Bandai. Though of course there's no reason to suspect they will not sign up in the fullness of time.