This was touched on by the study mentioned in the article which researched millions of headlines -- there was a interesting study from Wharton School of Marketi

This was touched on by the study mentioned in the article which researched millions of headlines -- there was a interesting study from Wharton School of Marketing titled What Makes Online Content Viral [1] that demonstrated which emotional valences led to readers sharing content, and the biggest predictor was anger. Interestingly the valence that led to the least amount of sharing was sadness. [1] http://opim.wharton.upenn.edu/~kmilkman/2012_JMR.pdf http://opim.wharton.upenn.edu/~kmilkman/2012_JMR.pdf