these cards worked just as fine as the sony official cards. if you open one of them and have a look, it actually has real magic gate chip and samsung flash memory chip which is also used by sony official memory cards.
it's surely a fake, yes. these cards were not made by sony but by some factories in china used pretty much the same components as sony used. sony has so many factories in china, it's not hard to imagine that the magic gate chip could just have leaked out or simply illegally re-produced.
Datel took many years to learn how to bypass the magic gate and finally made their maxi memory cards. these chinese factories can only use the leaked magic gate chip to produce the memory card. with the magic gate chip, it's easy to make 16mb/32mb/64mb cards and they work just as good as the sony official ones.