Are sites doing enough?
There have been suicides that were allegedly connected to Ask.fm.
In April last year, British schoolboy Josh Unsworth, 15, was found hanged in his parents' garden. His family says he endured months of abusive messages on his Ask.fm profile.
Three months later, Scottish teenager Daniel Perry hanged himself; and two months after that, 12-year-old Rebecca Ann Sedwick from Florida committed suicide.
There is some evidence that both had abusive messages posted on their Ask.fm profiles.
Anonymity apps have come under fire even as their popularity soars.
Two-year-old Whisper, for instance, is said to have "many millions" of active users. The site and app allows users to post secrets about themselves. It is said to have collected US$24 million (S$30 million), according to Forbes.
Secret is meant for sharing secrets within your circle of friends anonymously. So that secret out there could technically be about you, even if it's a friend posting it.
Ask.fm representatives have said that the application is merely a tool and it cannot dictate how people use the site.
But it has instituted measures where users can block anonymous questions. Users can also report behaviour that is violent, pornographic or contains hate speech. More recently, it has hired human moderators.
Whisper has a team of moderators and bans posts that contain names (except for celebrities). If someone mentions suicide, Whisper hides the post and sends its author suggestions about where they might get help.
Whisper also seeks out authorities when content suggests potential child abuse.
In comparison, Secret does the least as it relies on members to flag inappropriate content.
But Mr Jim Steyer, CEO of child advocacy group Common Sense Media, doesn't think any of the apps are doing enough.
"These are the platforms through which some of the worst cyberbullying is happening," he says.
His website commonsensemedia.org advises: "If your teens do use the site, they'd be best turning off anonymous answers and keeping themselves out on the live stream - and knowing how to handle abusive behaviour if they do run into bullies."