This is a subjective question for the most part however, as it depends largely on how you think of the word ‘safe’ and define its context and boundaries.
Safety is not just in the games companies’ hands, but also in the parent’s hands.
Educating children to use the internet responsibly, in conjunction with safety measures implemented by both online game and media companies as well as parental filters, can help to provide a safer environment for children online.
Moshi Monsters is one example of a virtual world for youngsters where safety is paramount. One of it's suggestions is for parents to create their own monster so that they can test out the safety of the site for themselves. Also, it sets out a list of guidelines for children to follow on how to use the site safely.
An example of this is the online help tells the children not to give out any personal information to anyone (such as real name, location, telephone numbers), and if the youngster runs into any trouble, then they instruct the child to contact them with directions as to what the problem is.
Moshi Monsters and other various online worlds will be required to have in place systems where the information being passed around from player to player is stored and accessible to the relevant authorities should the need arise.
They will also likely have in place tracking tools to monitor the content of such messages to attempt to enforce active monitoring of virtual world content that is being generated by the game's population.
This can be a great help in protecting children online and making a safe virtual world for children of the age of 10 and up.