Snapchat's rise from obscure app to Facebook rival charted in How To Turn Down A Billion Dollars

Snapchat is the great dividing line in the social media ecosystem: the old, with their fuddy-duddy Facebook, don't understand it and do not use it; the young, with their selfies and sexting, have taken to it with alacrity, their daily usage figures far exceeding that of any other app.

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