I believe warning labels on products do contribute to a reduction in a persons personal responsibility for their own safety. This of course has more to do with the people that were the source of the problem who caused those labels, rather than the people who usually read them. I personally find them laughable. I already know that coffee is hot and I also know that I shouldn't put a plastic bag over my head. Most of the warning labels in our society are not needed, but they are there because someone was stupid enough not to notice the danger.
Warning labels on products do not contribute to reducing people's personal responsibility for their own safety. This is because most people are not scientists or experts on what they consume on the market. Labels with warnings increase their personal responsibility because they are then aware of what they are consuming without excuse.
Without warnings on labels of things that could be dangerous, such as cigarettes for instance, the population gets complacent and is not really sure if it is harmful. Stating that it is when that is a certainty just puts the onus back on the person, who certainly is responsible for making his or her own choice.
Personally, I don't think warning labels on products are there to help people be more responsible, or reduce people's responsibility for their own safety. The warning labels are often there as a means to protect the company. If a company can demonstrate that they warned people for anything wrong that happens, it reduces their liability in the case of accidents. So it's really to protect them from frivolous lawsuits.