The California DOT has found this out the hard way. A lot of the iron and steel work for the new San Francisco Bay Bridge is being made in China, and CALTRANS has had one hell of a time monitoring quality of welds for this job.
A major refinery in the Midwest prohibits the purchase of valves and piping materials from Mainland China. Quality problems, as in casting being very questionable, where the risk would be prohibitive. BTW, the management of the company is quite libertarian.
One major pharmaceutical company tried moving production to China, and found the exact kind of quality fade cited in this article.