PSP Dead Pixel Problem...

[Ouroboros]

A while back I worked at Gamestop. While working there I encountered a problem with the PSP that I hadn't heard of before. I guess a certain percentage of PSPs will get a "dead pixel" or several dead pixels on the screen at some point or another. The dead pixel is just a very small grey square that doesn't show the image as it should.

My question then is this, is this still a problem found in new PSP devices or was this something that was fixed? How many people have experienced this problem and how long ago was it/when did you buy your PSP?