[quote name='Tygamr']Actually, you've got it backwards. You can have one account on several memory cards as long as they are used on the Vita the account is registered to. You can also have up to two Vitas registered to a PSN account, but I don't know if you'd be able to share a memory card between the two.
I think I know where you got that from. You can only have one PSN account per memory card according to Sony, though I have read stuff to the contrary- apparently, you can store content from multiple accounts on one card, but you cannot access games from the inactive accounts. So in order to use the games bought with the currently inactive accounts, you have to restore your Vita to make the current account inactive, and the account with the content which you want to play active.[/QUOTE]
Oh wow, I didn't know this either and I have a Vita. I thought you had to re-format or restart the system or something every time you entered a different memory card.