Led by Sequoia Capital's Growth Fund -- with existing investor Accel Partners also participating -- AdMob intends to use the cash infusion to expand its market position in mobile advertising. The company has posted strong year-over-year growth. In fact, the mobile-advertising platform more than tripled the number of ads served on a monthly basis to 4.5 billion in September.

AdMob's publisher network now includes more than 6,000 partners worldwide, including MySpace and MovieTickets.com. In September, AdMob ran more than 25 campaigns for brand advertisers, including CoverGirl, Toshiba and Comedy Central.

"Today AdMob reaches more consumers on their mobile phones through our publisher network than any of the major Internet portals or search services, and this is just the beginning," said Omar Hamoui, founder and CEO of AdMob. "We chose to raise this new round of funding to continue to grow both the mobile-advertising market and AdMob's clear advantage in it by investing in the technology, operations and team that have set the bar for the mobile industry."

Big Plans for Big Cash

AdMob plans to hire local staff in key markets and add new language interfaces, with an emphasis in Western Europe, India, South Africa, and Japan. It also hopes to deepen its investment in the company's mobile-technology platform, including its targeting, optimization and ad-serving algorithm; expand offerings for both publishers and advertisers; and increase its market share in the U.S. by boosting AdMob's sales and business-development teams.

AdMob has surpassed the largest names in digital advertising to become the world's biggest mobile-ad network in just two years, according to Jim Goetz, a partner at Sequoia Capital. As he sees it, AdMob has tapped into the exploding market of publishers creating mobile content for consumers and the advertisers eager to interact with them.

"AdMob is well capitalized and has achieved cash-flow positive results, giving them a unique opportunity in this difficult economic climate to aggressively capture market share," Goetz said. "They have some of the same qualities that we saw in Google, Yahoo, YouTube and Apple, including their exceptional team and powerful technology platform."

An Uphill Climb

Greg Sterling, principal analyst at Sterling Market Intelligence, is a bit surprised that AdMob is cash-flow positive, but he wasn't at all surprised by the funding because it's easy for venture capitalists to put money into a company that's already successful. But AdMob may have an uphill climb.

"Despite AdMob's success, and the fact that there are between 40 million and 50 million mobile Internet users in the U.S., most advertisers are not doing anything in mobile today," Sterling said. "It's viewed as an unproven or experimental medium by most traditional advertisers."

The recession, Sterling added, has created a kind of "deer in the headlights" effect among some marketers: They're not going to do anything new or different and are trying to consolidate ad spending around "tried and true" media.

Still, Sterling said, for those marketers that are taking advantage of mobile, there are some real benefits of being early -- and not facing the kind of competition that will come later as more marketers start to appreciate the value and importance of the new medium.