The Washington Post describes the phenomenon related to overwarning:
"The national recall system that's in place now just doesn't work," said Craig Wilson, assistant vice president for quality assurance and food safety at Costco. "We call it the Chicken Little syndrome. If you keep shouting at the wind -- 'The sky is falling! The sky is falling!' -- people literally become immune to the message."
(via Wolfman, whose post doesn't acknowledge to what extent Public Citizen and its allies have contributed to the problem, or the public-policy implications for current failure-to-warn law)