This is a very simple way to find out if your memory is fake or not on your PSP.
 
1) Go to Memory Stick Menu (Under Game)

Bigger Image Here: http://img241.imageshack.us/img241/8895/startrv0.jpg

2) Press the Triangle and the tab Information appears.

Bigger Image Here: http://img241.imageshack.us/img241/3074/infodh5.jpg

3) Press X. If you see that Magic Gate is Supported then you have a Genuine memory. If it says Unknown then you have a Fake.

Genuine Memory

Bigger Image Here: http://img241.imageshack.us/img241/882/genuinebr2.jpg

Fake Memory

Bigger Image Here: http://img241.imageshack.us/img241/4897/fakele6.jpg