By NICK BILTON

Snapchat allows people to take and send a picture, then control how long it is visible by the person who receives it.
People once took photographs so they could capture a moment for themselves and keep it forever. Then digital cameras and cellphones turned photos into something more ephemeral and more easily shared. But as the case of Anthony Weiner demonstrated, photos that are shared but are not meant to last, sometimes stick around.
AFP Relax
A new study, announced on Wednesday, finds that nearly one in five teens have sent sexually explicit photos on their mobile phone -- many of them with little or no awareness of the possible psychological, social, and sometimes legal consequences of doing so.