Okay, we put aside that point about people who are pros and people who have contras opinion about Facebook. There is a case in Jombang, East Java. A female senior high school student was being kidnapped by someone she knew via Facebook. The details of this story can be read in this link http://www.beritajatim.com/detailnews.php/8/Peristiwa/2009-10-23/47853#.
Based on that story reported by Yusuf Budiono (the reporter of Beritajatim), the girl was making a friend with a man via Facebook. After that this 16-year-old female student went with the man to Bali. Then there was no contact anymore with her family. Of course her family was in terrible sad and very shock (may Allah help them). A source said that the girl has become a victim of human traficking.
So be careful my friends...