Vita firmware 1.80 ties memory cards to a single PSN account, according to a report on NeoGAF, which means users can no longer store data from multiple accounts on one memory card.
Those who try to switch accounts will be met with the following message:
The memory card inserted in your system is linked with the following Sony Entertainment Network account.
To use the memory card with your PS Vita system you must format the memory card.
If you format the memory card, all data on the memory card will be deleted.
Those who try to switch accounts will be asked to format the memory card, which will erase all data stored. expensive memory cards.
Sony never specified multiple accounts could be stored onto one card, but this may come as an inconvenience to users as they will have to purchase more memory cards.
Ergo, be sure to back up any data you have on your memory cards before installing firmware 1.80.