Research has shown that more than a quarter of eight to 11-year-olds who are online in the UK have a profile on a social network site.
With none of the websites actively enforcing a minimum age limit, the watchdog Ofcom says parents need to keep an eye on what their children do online. So what do parents think?
ROGER FROM SOUTHAMPTON
I have worked in the internet for the past 15 years but I resigned as the director of a company that set up a social networking site in 2003. The company wanted a network aimed at young teenagers and I felt this was unacceptable.
I was told by ex-colleagues that it took 24 hours for them to find their first paedophile had registered and was trying to groom kids. It ended up with the police getting involved.
My daughter uses Bebo and despite using a profile with anonymous settings ticked and not using her real name, I was able to show her how I was able to find her school, name, form, where she lived and view her profile all without even having to register on Bebo.
I think the only way to protect your kids is to have an honest relationship and speak to them about the issues.
The danger is when you overreact then they will become secretive and actually blocking them would be to cut down on their social life, an important part of growing up.
Every month I ask my daughter for a list of all the people she has connected to and I say to her who is this ? Do you know who this person is ?
A FATHER FROM NORTHERN IRELAND
A number of children in my son's primary school set up a hate page on Bebo about him.
When I complained to Bebo the response I got was: "If you don't like the page don't look at it." They couldn't have been less helpful.
I complained to the police and a brilliant community policeman went round to the houses of the children who had set up the page and it was pulled.
But until the police got involved they did not remove a single person who set up or contributed to this page, despite being informed that they were all aged 10 or 11.
MONA ZAHOOR FROM SURBITION, SURREY
I have a 13-year-old son and a 10-year-old daughter and the trick is to stay one step ahead.
I am not from an age where I knew what Facebook and Bebo were. So I made an effort to find out for myself and I made sure I was active on Facebook before my children wanted accounts for themselves.
When they wanted to go on Facebook I helped them and made sure the privacy settings were adequate.
We are now Facebook friends, and I monitor activity every day. I do check who their friends are and make sure they don't change their privacy settings.
I think social networking sites are perfectly safe as long as parents stay one step ahead. As a parent you have to keep up with the times and not let your children become social outcasts because you do not allow them to use these sites.
MATTHEW HIGGINS FROM COLWYN BAY, CONWY
I am a Scout leader and last year a 12-year-old girl in my Scout group registered on a lesser-heard-of social networking site and spontaneously put her MSN messenger address in.
Within hours someone had added her and was sexually harassing her online. When I heard about this it was reported to the Child Exploitation and Online Protection Centre.
It is clear that this incident is not isolated.
Particularly since then, but also a little before, I have made educating young people about sort of 'dos and don'ts' online something I really care about and take quite seriously.
I use Bebo and Facebook myself to some extent, the difference is that I am aware of how to safely do this.