I was reading a blog when I noticed a news headline on my browser dashboard about a girl getting threatened on facebook.
She was a cheerleader in high school and most probably one of the IT girls. She received an invitation to be a friend, on her facebook account, by a schoolmate who she was never friends with. This guy was the nerdy type and probably very unpopular during their high school days.
The first few PM's (personal message) were friendly until it got to a point when he was sending messages that were too uncomfortable for her already. She then sent a message with STOP written 100 times. That's when the scary emails began.
She then created a facebook page "If I get killed tonight, this is why" and posted all threatening messages there. Fortunately, her mom is a cop. Her mom helped her report the incident to the right authorities. The guy is now in jail.
My two cents? Facebook is safe to use. It's the facebook user who's making it unsafe. Don't put personal informations about yourself, don't broadcast your daily activities and be a more responsible facebook user. That's all you have to do to be safe online.