It's not that they are not Sony, it's that they are unlicensed. All licensed cards must be produced to spec guarantying comparability with all games. Unlicensed cards do not, and may be incomparable ...

U.S. game players are finding it tough to buy memory cards, the most common add-on for Sony's PlayStation 2 video game console. The 8MB memory cards plug in to the PS2 and are necessary for people to ...

Somewhat related, I think it was about a month ago that I couldn't find Sony PS2 memory cards in stock anywhere. Not sure if that's still the case, but if so, I did find them in stock at ...