Please don't blame the politicians who are trying to protect us from big business over big business that doesn't care whether they poison us as long as they make money.

There isn't an effective mechanism to determine how carcinogenic or teratogenic every application of every substance is. There's simply way too much variability. Knowing that a product contains chemicals from California's list (roughly 900 I believe) of chemicals known to cause cancer or birth defects gives you the information you need to make decisions about how you use it. If something has this label, don't let your baby put it in its mouth, for example, or don't sand it down and breath in its dust, or wash your hands after you use it before you eat.

This warning is fantastic and is not supposed to give you all the information. It only tells you that one or more known dangerous chemicals are present in a product, which is still invaluable information.

What kinds of carcinogens a product actually contains can only be determined iff it is submitted for testing. Making the testing mandatory for all out-of-state products would be economic suicide. Assuming yes unless proven otherwise is the safest strategy that gives consumers at least some level of informed choice.