The hard to spot fake controllers are a big problem as they're poorly made and will make you worse at the games as the sticks are not perfectly linear when moving them and this makes driving and shooting games much harder. For example i'm usually pretty good at both genres and was using a fake someone had accidentally bought and I was terrible
Bad times on racing and always dying on shooters, just doesn't quite point where you want it to.
Lots of web pages about to help you spot fakes, like if the '3' on the 'dualshock 3' on the top ends right where the usb starts to recess you've got a genuine most likely. The click when pressing the sticks on a fake is also very loud and sounds more like a clink, on a genuine the stick doesn't move very far down when pressed, is a bit quieter and lower pitch. Though this one is hard to test without a fake there to compare it to.