Not too long ago, my daughter was victim of a message campaign by some classmates that showed her in a poor light. In fact, some of the messages were downright false and malicious but they were posted people subscribed to the poster anyway. There was no way to remove them although we tried to send an email to the provider. There was little opportunity to get the girls who had posted the messages to take them down. Later, they regretted what they had done but it was too late, and no adequate way to repair the damage. One cannot undo things on social networks. Kids are young and cannot take back things they do like they take back words, and this is the problem my daughter faced to everyone's regret.