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Yolo lets snapchat users request anonymous messages from specfic friends or the wider public.
Yolo - an app that lets anonymous questions be posed to Snapchat users - has become the most-downloaded iPhone app in the UK and US just a week after its release.
However, the viral success of the product has raised concerns.
Previous anonymous online Q&A services have been blighted by abuse and bullying.
"Apps such as Yolo that allow anonymous comments could be easily misused to send abusive or upsetting messages," the National Society for the Prevention of Cruelty to Children (NSPCC)'s Andy Burrows told the BBC.
A US-based child safety campaign group has also suggested that Yolo's age rating is too low.
Yolo is one of the first apps to have been built using Snap Kit - a software creation platform launched last year by Snapchat. The kit lets third-party developers integrate their products with the social network.
The app works by letting people post a graphic inviting others to "send me anonymous messages", which is superimposed over a photo.
The post can be sent to a specific set of Snapchat contacts or attached to a Snapchat Story and shared more widely.
Those who see the request can then send an anonymous message via Yolo itself. If the original poster decides to respond, their reply is in turn posted back to Snapchat.