From The Verge:
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."
Because letting a friend quickly borrow a Vita to play with, customize and experience wouldn’t be good advertising at all. No way.
Just Kevin Butler. Butler all the way. He knows how to make new hardware crazy popular.
</sarcasm>