AdSense has much lower margin compared with AdWords because Google has to pay publisher for displaying the ads. In the early days, (AdSense revenue around 1B) I

AdSense has much lower margin compared with AdWords because Google has to pay publisher for displaying the ads. In the early days, (AdSense revenue around 1B) I remember google was almost paying every penny they got from AdSense back to the publisher. Only later, they started to make money, but still capped by the competition from microsoft/yahoo. Facebook entering the AdSense market? It won't generate a lot of profit for facebook. The true profit engine for facebook is still the facebook site.