Developer Smoke just released memcardswap, a tool that lets you swap memory cards between accounts without a need to reformat. This technically lets you use the same memory card for several accounts on your various PS Vitas. This is particularly useful for people who use different accounts (typically one account for homebrew-related stuff, another account for normal gaming).
What is Memcardswap for PS Vita?
Memcardswap just deletes ux0:/id.dat from the memory stick and replaces it with an empty one (the code is extremely simple*), a method that has been known for more than a year when it was revealed by Major_Tom and Mr.Gas. This tricks the PS Vita into believing the memory card is “new” and therefore does not need to be formatted. Next time the card is inserted in a Vita, id.dat will be re-generated for the current account, without formatting anything.
Of course, this does not magically transfer the licenses! If you have a game owned by User1, and try to run it from User2’s account after swapping the card to user2, this will not work. Except for unsigned stuff such as homebrew, of course.
Technically, you could upload an empty id.dat file yourself from the ftp with molecularShell so this app is not an essential tool, but it is a quick shortcut that will be useful for those of you who regularly switch between accounts.