semiconductors
Counterfeiting semiconducters is biiiiiig business.
There are multiple mechanisms : relabeling parts to a higher clockspeed ( especially memories ! and of course cpu's )
Parts that were destined to be scrapped ( out of spec devices. for instance a procsoor in idle is supposed to draw no more then 60 mA. due to process variations some draw 100 mA. these are rejected. even though they work normally they are 'borderline and prone to early failures . manufacturers dont; want these out on the streets becaue they will come back as returns under warranty !. whole truckloads of such things get stolen .labeled and sold ( such devices are not labeled )
rebranding parts. selling cheapass memories from vendor x , and labeleing them with the name of a premium vendor.. instant $$$ ...
And then plain counterfeits. 4gb flash chips that only contain 2 gb ...
this happens with parts that are in short supply. all fo a sudden 'someone' ( mostly in the far east' has a lot of a couple of thousand parts that he 'no longer will use' becasue the product he used them in has been cancelled. so they end up on auction sites ...
Assembly houses that need parts and can;t get them in time may be tempted to buy whatever they can get to keep production flowing.. and sometimes get royally shafted by such 'brokers'. by the time yiou want to file a complain the broker has dissappeared. company closed , office turned out to be a answering machine tied to a cell phone in a trainstation locker somewhere ...
sometimes its parts that are sold as leadfree but actually are relabelled parts with lead in them !. someone had a huge stock of a certain part that is in high demand . unfortunately its a part that is not RoHS compliant. simply relabel them and sell them as RoHS compliant !. buy cheap . sell at full price. instant $$$
if you want to know more : here are some websites with examples of counterfeit chips.
http://www.designchainassociates.com/counterfeit.html
this webpage has pictures and real examples of counterfeit parts :
http://www.eetimes.com/showArticle.jhtml?articleID=201201791
its a real plague, both for buyers (they get wrong parts or altered parts with lower reliability or unusable parts like not rohs compliant parts) and manufacturers becasue they get a bad name or have to deal with stuff that returns under warranty ....
So there you go, now you know. I am working in the semiconductor business and have personally seen 2 different counterfeits.
Mine's the Class-i Cleanroom Suit.