They are supposed to
have the appropriate quality control processes in place
to prevent crap from getting through. And a responsible
US company would stop
doing business with any vendors that try to pull such stunts.

Companies don't find out a China manufacturer switched something until
the products have already been imported and sold. They will NOT allow
inspection. Or they set up phony assembly lines for quality
inspectors. Out and out deception and fraud! See for yourself...

Read the book: Poorly Made in China: An Insider's Account of the
Tactics Behind China's Production Game...
http://www.amazon.com/Poorly-Made-Ch.../dp/0470405589

Lethal tampering with food or drug ingredients (to say nothing of lead
paint in toys and poisonous toothpaste) from China seems to be
business as usual....
http://www.utsandiego.com/news/2009/...roducts-china/