ARE CHILDREN SAFE!!!!!

I was watching the news this morning about a 17year old girl who was talking to a man who posed as a teenage boy on facebook. They met and he raped her then killed her.
He was a man of 33 and is a convicted sex offender.

My heart goes out to her parents, the question is what was she doing going to meet someone she had never met, surley at 17 she should have known about the dangers of meeting someone who you've only talked to online and have never met..

Where do you draw the line children need there own space and freedom but you can't help worrying about them 24hours aday. As a parent myself im quite strict on who my child sees, where he is, who's he with, i constantly worry all the time because there are so many bad people out there.
If I was asked which was safer let my child go to the corner shop on his own or let him go on the internet alone, my answer would be neither because there have been so many children abducted and murdered by walking home from school, going to the local shops even playing in their own back gardens.Its the same for the internet, there are so many pedofiles and sex offenders praying on children over the internet posing as kids themselves.
Why are there so many sex offenders, pedofiles on our streets? I think its because the law is to soft on offenders and on many occasions they get 5 years in prison and are let back out on the streets knowing that they are going to commit crimes again, whats worse they sometimes let sex offenders and pedofiles live near schools and childrens play areas WHY???