Schneier quotes this excellent article:
Although statistics show that rates of child abduction and sexual abuse have marched steadily downward since the early 1990s, fear of these crimes is at an all-time high. Even the panic-inducing Megan's Law Web site says stranger abduction is rare and that 90 percent of child sexual-abuse cases are committed by someone known to the child. Yet we still suffer a crucial disconnect between perception of crime and its statistical reality. A child is almost as likely to be struck by lightning as kidnapped by a stranger, but it's not fear of lightning strikes that parents cite as the reason for keeping children indoors watching television instead of out on the sidewalk skipping rope.
And when a child is parked on the living room floor, he or she may be safe, but is safety the sole objective of parenting? The ultimate goal is independence, and independence is best fostered by handing it out a little at a time, not by withholding it in a trembling fist that remains clenched until it's time to move into the dorms.
Meanwhile, as rates of child abduction and abuse move down, rates of Type II diabetes, hypertension and other obesity-related ailments in children move up. That means not all the candy is coming from strangers. Which scenario should provoke more panic: the possibility that your child might become one of the approximately 100 children who are kidnapped by strangers each year, or one of the country's 58 million overweight adults?