Anonymous online communication offers some benefits. However, it can also be a ground for online bullying. It is a function that can be and has been misused. It allows children the opportunity to separate their actions from their consequences. Users have used annoyminity to be cruel and hurtful. Ask.fm and bullying have been linked in some specific news reports about cyberbullying.
Talk to your child about bullying - how to behave with respect towards others and what to do if they experience cyberbullying themselves or witness it happening to someone else. Encourage your child to always speak to you or another trusted adult if they have any online concerns.