Google revenues

I was just comparing Google's market capitalization with their revenues. Their market cap is close to 160 billion dollars but their revenue is just $11 billion. With $8 billion of that coming from Google AdSense alone. I would like to get your viewpoints on Google's business model. It looks like only their ad networks have a decent revenue model. Compare this to the revenues of the top 4 advertising agencies including WPP, Publicis who have 1/3rd Google's market cap and thrice their revenue. The markets are saying something about online taking lead over offline in the coming few years