It wasn't that long ago that you would ask a young teenager about computer stuff, but these days it's even younger. According to NSPCC, a charity organisation in the UK, children as young as five should be taught about safety online.
I can attest to this, as my six-year-old niece is happy using a tablet, smartphone and computer to play games and browse sites. To put it another way, the very young are now getting connected and while their focus is typically on child-like sites this opens them up to the wider and darker parts of the internet.
There is a nasty element out there that will, for example, coerce this age group into making their own explicit photos or films. In the older age groups sexting is becoming more common and it is easy for all age groups to suddenly find themselves looking at porn. Years ago sneaking into an R-rated movie was a badge of honour for 17-year-olds, these days watching porn is so passe that the self-made images are perceived as the only way to earn "respect". The predators are happy to prey on such misplaced ideas and in a busy world parents either don't have the time or are simply unaware of the issues.