It happens. It's annoying as heck. But if you're not looking for it, you can block it out. I usually have to be really immersed to block it out myself.

my Tiger Game.com has lots of dead pixel lines across the screen. As long as you still see enough, you can keep playing!

i have some on the botten left corner of the top screen

12 years later and my original o3ds still dosen't have any dead pixels.

...sorry i think that came out a bit rude.