It depends on the age of the child, as most social networking sites, such as Facebook, Bebo etc, don't allow anyone under 13 to join. If you have a 13 year old who would like to join, for example, Facebook, you should have a talk with him or her about the possible dangers of sharing information with strangers online. You can learn about some of the pitfalls and the best ways to deal with them here.

At the moment Facebook is looking at ways of creating a network that can be used by children under 13. These might have to be linked to the parents' accounts to make sure that the parents had overall control, so your child couldn't get in touch with anyone without your knowledge, for example. However, there are a lot of legal issues with this, and it may not happen.

There are networks aimed at children such as BunkiMunki, but there is no reason to think that these networks are safe or that it is a good idea for children to use them. It's really best if under 13s don't use these networks.