“Q: How many PSN account can be set up on a Vita system?” GAF member mehdi_san wrote. “A: Only 1 account. If you want to use a different account, you need to format the system to factory settings.”
Some PS3 and PSP owners have separate accounts to pick up games and demos from other regions. This move means those players will be out of luck when it comes to playing Japanese titles on their American systems, or vice versa.
On the bright side, a Sony representative recently told Thrifty Nerd that Vita titles on PSN would cost up to 40 percent less than their retail counterparts. It’s some decent savings that could make up some of the ground lost by recent Vita revelations. Proprietary memory cards required to save certain titles, an expensive UMD Passport program missing many key developers, and a lack of support for PSOne Classics are slight issues alone, but are starting to add up for some early adopters.
EDIT: So the limit on PSN accounts is actually linked to the memory card, not to the Vita, according to Eurogamer. Still annoying:
The PlayStation Vita is not limited to a single PlayStation Network log-in, as widely reported last week, Sony has confirmed.
However, you will need to either restore factory settings every time you want to change accounts or buy two separate proprietary memory cards.