nVidia's customers are OEMs in that particular case. You should talk to Apple, HP and Dell for not checking what stuff they placed in their own product. If that was a defect in every single unit (like people tell) then someone at those companies should have noticed way before selling the notebooks. You just don't make a product without testing it a little bit before selling.
nVidia did wrong in not keeping an eye on the production. They should have had better QA to spot such problems and stop shipments.
And then there are the nVidia's contractors, who did the shoddy job at producing the chips (nVidia, much like Intel and AMD doesn't manufacture chips in-house).
There was a long chain of errors. nVidia is certainly to blame because they didn't had enough controls to prevent this from happening, but the real production of shoddy chips was done by third party manufacturers, and by the OEMs witch didn't have a decent QA policy or simply didn't care. All those products are for the consumer market anyway.