Tim Armstrong has certainly come a long way from Snowball.com. The teen-focused, very late '90s dot-com-era firm was his last stop before joining Google in 2000, when he became the start up's national head of sales. Today, he oversees one of the fastest growing revenue generators in the media business— wielding significant clout at the company for which the term "frenemy" was coined.

Over the past six years or so Armstrong has become Google's public face on Madison Avenue. And during that time, he's helped sell pay-per-click ads, which still serve as the search giant’s c o re revenue driver. This past second quarter, Google pulled in $3.8 billion, a 58 percent increase over second-quarter 2006 revenue of $2.46 billion, with the vast majority of those dollars coming from advertising.

While many might expect that running ad sales at a company that is growing at that rate would be easy, Armstrong has had to deal with serious operational headaches, as the company has staffed up rapidly.

"Most companies the size of Google have 10, 20, 30 years to build this kind of structure," said Rob Griffin, senior vp, head of search at Media Contacts. "You have to give him credit for surviving the craziness."

And Armstrong's oversight extends well beyond sales—when CEO Eric Schmidt needs to smooth things over with Rupert Murdoch, he brings Armstrong along—and he helped shepherd the $1.65 billion deal for YouTube and the pending $3.1 billion deal for DoubleClick.

These days, one of Armstrong’s biggest challenges, besides managing growth, is managing expectations. "Google is at the top of the food chain in online advertising," said Ellen Siminoff, president/CEO of the search specialty agency Efficient Frontier. "He's in the position of many people wanting more from Google than they can possibly deliver. He's done a really nice job of representing Google’s position, while handling himself with a certain amount of grace." — Mike Shields