Memory cards / thumbdrives are the canonical example here, I think. The fakes are plentiful, and comingling ensures that you are playing roulette every single t

Memory cards / thumbdrives are the canonical example here, I think. The fakes are plentiful, and comingling ensures that you are playing roulette every single time you purchase one, and the fakes are good enough that they'll stand up to visual scrutiny unless you know exactly what you're looking for, and sometimes not even then.