I think we all agree on that. I cannot tell you how many riders I see wearing helmets incorrectly, falling over to the side, off the back of their head. Generally, I've found that these are either new riders or people who have been riding for 20+ years. The first group usually appreciates some instruction on how to fit a helmet correctly and the second group, well, not so much.
This is one of the things we do in our bike workshop every spring. Either me or DH loosens our helmet and slides it back on our heads to show the "incorrect" position. I'd say at least 50% of the participants exclaim, audibly, "I didn't know that."