I gave this talk to a group of MBA students at Cornell University's Johnson School in a class called "Current Topics in Marketing". This walks through the evolution of online advertising and how we got to the new chapter, brought about due to the rise of Facebook: "word of mouth at-scale". We then explore what that means, how it works, and leave with a couple of examples. Special thanks to the folks at Nanigans for all the slides. *Please note: some slides did not convert to the Slideshare format properly, so contain missing content. I will try to fix.