Once upon a time, future PlayStation Vita owners were bummed to hear that PSN accounts were tied directly to the hardware in such a way that a full factory reset was required to switch users. Sony quickly rebutted with a statement that claimed accounts were tied to memory cards — meaning one Vita could be home to any number of PSN accounts provided the external memory was swapped in and out. Turns out both reports were correct: as of today, Sony has clarified that the PSN accounts are actually tied to both memory cards and hardware.
According to a Sony representative speaking to Wired, "if a second person is using your Vita, it's not just a case of switching out memory cards, it's clearing out all of your saved data on the Vita itself when you do the factory reset." We reached out to Sony and got our own similar statement, printed below. So we're back to one Vita per person, not per household — best to know such things before the launch, right?
Like PSP, PS Vita is intended to be played by only one user as a personal portable entertainment system. As such, the spec is set so that only one PSN account will be connected to one PS Vita hardware.