But is it possible that part of the reason crime is down is because of Stranger Danger?

Yes. This is a really soft question. Sure, part of the reason that crime is down could possibly be due to stranger danger.

On the flip side, over-parenting has negative consequences on kids who have no freedom. I believe the same poll had said that most kids had never walked down a grocery store aisle by themselves and weren't allowed to play outside in front of their house w/o a parent.