I was looking for something else on Flickr, when I came across a bunch of photos posted by someone named "missing person net" 寻人网.  Since April 21, 2005, "missing person net" has been posting photos of missing mainland Chinese people on Flickr. 

The most recent was posted on May 28, 2007:

Na Kexin, female, 14 years old, born 1/19/94, inadvertently got lost. Home address: Heilongjiang province, Youyi County, Xinglong Town.  Distinguishing characteristics: thin, 1.7 meters tall, medium length hair, fairly goodlooking.  Contact number: 13555103059.  Family guarantees deepest thanks to those who can provide information.

After Baidu'ing the term "missing persons net" this site came up: 110 missing persons net.  It posts photos of people who others are looking for.  It also has a section called "successful cases," meaning those which have been solved, which are divided into the following categories: Left on Own Accord; Reasons Unknown; Cheated or Kidnapped (all children); Lost Way (quite a few older people); Lost Touch With Friends and Family (only 3 of these); Orphan Looking for Relatives (only 3); Urban Vagrants (3 young boys). 

These cases provide the briefest glimpses of a different world:

Name: So-and-so Liu (Liaoning)| Posted: 2006-5-8
Missing person notice: Liu So-and-so, male, age 16, Liaoning Province Benxi City, left home 9/19/04, family members posted notice on this site 5/8/06.  8/2/06 family notified this site that Liu So-and-so had returned safely home. 

Advice: Parents should communicate more with children, discover problems in a timely manner, and resolve problems in a timely manner. It is to be hoped that Internet cafes will not allow minors to enter, that work units will not employ child laborers, and that police departments will take more responsibility.