Years ago I got caught buy buying a cheap 32Gb USB memory stick from eBay. It appeared to be 32Gb, formatted as 32Gb, but in reality was 8Gb. Somehow the scammers had faked an 8Gb stick to make itself look like a 32Gb stick. It still works fine up to 8Gb and I've been using it for a couple of years with no problems, but it's clear that there are an awful lot of fakes around, almost all coming from China.
I've also bought (and tested) fake power MOS FETs from China. Some of these were clearly fakes from the markings being in the wrong place, some were visibly fakes because the manufacturer only made those particular parts in Mexico, not the Far East, yet the fakers had put the wrong country code on the package. Some of the fakes weren't far off the spec of genuine devices though. For example, I tested some IRF4110 FETs and found that they seemed to have the same voltage rating and a very similar Rdson (within my limited ability to measure this). Where they didn't meet the spec (apart from the dodgy package marking) was when it came to measuring the turn on time. Every single fake I tested blew when I tried to turn it on under load fast, whereas the genuine ones were fine. Clearly the fakes just couldn't meet the dV/dT switching time spec.
I have a friend who lives in Shenzhen, and who regularly visits the massive electronics market there (this place:
http://www.evilmadscientist.com/2009/a-visit-to-the-electronics-markets-of-shenzhen/ ). He's local and knows his way around there, so can usually get me stuff that's "real" and send it on. Even then he's been caught out a few times with fake stuff. One example was some power controllers, where he assured me that he knew the seller and the power semiconductors were genuine. He was upset when I Skyped him to tell him they were fake and he went back to the seller. The seller just shrugged and said "but the price was good". There's a Chinese manufacturing philosophy that it's all about price, and that cutting any corner to get the price down is a good thing, even if the end result is a product that fails. For many manufacturers the reliability of their products is of low priority, the most important factor is price, as there isn't the same emphasis on consumer protection and people expecting reliable products there as there is here. That's changing, as Western companies set up manufacturing plants in China and set higher quality standards, but that goes against the traditional way Chinese business has worked for years.
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