Consumer Reports once did a review of jack stands. Those are little supports that you put under the axle of your car after you've jacked it up, so that you can work under the car. Every jack stand they reviewed had a warning label that said that under no circumstances was it to be used to support a car while someone was working under it.

The review explained that (a) Those labels were probably there because some lawyers thought it would make the manufacturers less likely to be sued if their product collapsed and killed someone working under a car. (b) They also said that their own lawyers told them that the warnings wouldn't make any difference at all, because if you were to heed the warnings, the product would be useless for the purpose for which it was advertised and sold.