"It started a ball rolling," she said. "There was a real momentum."

Barbara Friedman, associate professor of University of North Carolina's School of Journalism and Mass Communication, has said such "heinous crimes are always newsworthy" and "have been reported in the press for as long as there has been a press."

"As media became more plentiful and visual in the 1980s, child abductions and child murders allowed for the kinds of images that are at once intimate and universal -- like school photos and grieving families," Friedman said.

"The use of milk cartons as another form of media to locate missing children was a way to bring the issue into the family space -- the breakfast table -- heightening awareness as well as anxieties."

Etan's family and Adam Walsh's parents have been particularly media savvy, she said, as they kept their cases front and center before the public and law enforcement.

"They were strategically and actively engaged in cultivating their attention. And in the age of the 24-hour news cycle, there were more reporters looking for substantive news stories and more space to fill," she said.

The case raised consciousness but also stirred fear.

"I think it ended an era of innocence in this country," Allen said. "Parents around the nation saw how it happened and thought, 'But for the grace of God, my child.' "