Jonah Peretti, the founder of BuzzFeed, disclosed in a recent letter to investors that its traffic tripled over the past year, hitting 85 million visitors in August. Soon—thanks to our collective inability to resist such sugary listicles as "36 Things You Never Realized Everyone Else Does Too"—Mr. Peretti says, BuzzFeed will be one of the largest sites on the Web.

Until recently, though, BuzzFeed's towering traffic ambitions were held in check by a simple fact of global demographics. Everything BuzzFeed publishes...