Ofcom today released a report, highlighting that many children and young people are unaware of the dangers they face when using social networking sites.

SOCIAL NETWORKING SURVEY
49% of children 8-17 have an online profile
22% of 16+ have an online profile
On average adults have profiles on 1.6 sites
63% of 8 to 17-year-olds with a profile use Bebo
37% of 8 to 17-year-olds with profile use MySpace
18% of 8 to 17-year-olds with a profile use Facebook
59% of 8 to 17-year-olds use social networks to make new friends
16% of parents do not know if their child's profile is visible to all
33% of parents say they set no rules for their children's use of social networks
43% of children say their parents set no rules for use of social networks
Source: Ofcom

You can read more about the Report at
http://news.bbc.co.uk/go/pr/fr/-/1/hi/technology/7325019.stm

One of the comments made was that many parents feel unqualified to advise their children on ways to keep safe on these networks.
Take a look at http://www.thinkuknow.co.uk where there is a page of guidance for parents.