It's hard to overestimate Google's authority in the digital space.

The search giant is estimated to account for 27 percent of the entire online ad market, according to eMarketer. Its share of total search queries is now more than 60 percent despite competitors like Microsoft throwing everything they have at the space, including paying people to use their product. And the company is poised to begin selling ads alongside No. 2 player Yahoo's search results, as long as the U.S. Department of Justice gives the OK.

Indeed, rarely has one media company enjoyed such clout. (Perhaps CBS during the 1954 upfront, when it had I Love Lucy, The Honeymooners and The Ed Sullivan Show—and there were only two other channels.) And holding the keys to this digital kingdom is Armstrong, who continues to command Google's ad growth despite several quarters of lowered expectations on Wall Street and dogged sorties by competitors. Armstrong's team hauled in $4.8 billion in revenue last fourth quarter, $5.19 billion in first quarter and $5.37 billion in second quarter.

Where Armstrong and co. lose points is YouTube, which has bombed as an ad vehicle despite its meteoric user growth. Two years after acquiring the Web’s largest video sharing site, Google has yet to roll out a killer ad product because of logistical snafus.

Still, Armstrong has continued to help Google make headway in the realm of traditional media. This month, he was at the forefront of a new pact with NBC Universal to test selling TV spots through Google TV. In addition, Armstrong is also bullish on mobile advertising when it takes off—particularly once Google's mobile phone software Android hits the market this fall.

2007 Rank: No. 2