How to swap your Vita memory card without formatting
Step 1: Create and overwrite/delete empty id.dat file
Depending on your firmware there are different ways to do this:
Fail-Mail trick - for firmware(s) 3.00 - 3.52
HENkaku - for firmware 3.60
Done! You should now be able to put this memory card into any other Vita without the need to format!
But remember that you will need to redo this process every time you want to swap again!
FAQ & Troubleshooting
After putting the memory card in the other Vita it restored itself.
No idea why. Shit happens.. :/
I can't start any of my games on the other vita?!
Thats normal. The games are still tied to your other account.
Is it possible to swap between a normal Vita and a PSTV?
Yes it is!
My e-mail shows a [?] instead of the photo symbol?!
Try resetting the Vita's mail account or resend the mail.