Think of the last time you visited a restaurant. How was the service? Was the waiter or waitress smiling? Could you pick up on their mood? Now think carefully. At the end, was the amount of gratuity offered influenced by how he/she made you feel? Of course it was. “Service with a smile” is a social contagion phenomenon similar to “Monkey See, Monkey Do,” whereby the emotional relevant stimuli is mimicked among members during a face-to-face interaction. What hasn’t been tested yet is whether this event holds true among social networks. Until now.