Google's Ad Revenue Mix

This chart says a lot about where Google gets its revenue and why it needs multiple hooks to get people to come to Google sites. Note that this chart is different from the numbers reported by Google because it allocates the traffic acquisition costs directly against the revenue from ads on other sites (AdSense). It also reminds us why we need to delve deeper than high-level statements and figures often bandied about in various places. 
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So, if Google is largely a destination site that depends on people visiting and spending time on its properties, then it needs to recognize the importance of social networking and threat from Facebook (and Twitter).  There are strong rumors that Twitter will launch an advertising platform soon.  Facebook already has its advertising platform. 
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And there is the mobile advertising battleground....