This could be the year that mobile advertising goes mainstream. Yesterday, Baby Breaker AdMob announced that it had received $12.5 million in additional funding from Draper Fisher Jurvetson's Growth Fund and Northgate Capital. Sequoia Capital was an early investor.

"As mobile Web and application usage continues to grow rapidly worldwide, and smart phones -- from the iPhone to the G1 -- gain in market share, we see a real opportunity to expand the mobile advertising market," wrote CEO Omar Hamoui in a blog post.

AdMob's backers obviously see the logic in Hamoui's plan. And why not? Apple (NASDAQ:AAPL) has sold 17 million iPhones, and its App Store has fed 500 million downloads to users. Roughly 15,000 applications were available for the iPhone as of this writing.

And the iEmpire has plenty of company. Palm's (NASDAQ:PALM) Pre shows all the signs of an innovator, and Research In Motion (NASDAQ:RIMM) is creating an applications store of its own. Google (NASDAQ:GOOG) and Nokia (NYSE:NOK) are also motivated competitors.

All of them will have access to better tools for localized content and hypertargeted ads, such as Loopt and BrightKite. Services like these explain why AdMob is serving 4.6 billion impressions via 6,000 mobile sites every month. Wireless community creator BuzzCity reported 50% growth in paid banner ads on its U.S. network during the fourth quarter.

It's always dangerous to proclaim anything the Next Big Thing, so I won't here. But in a market where very few deals are being funded, AdMob is landing the venture world's Biggest Fish.

So either mobile advertising is one of 2009's big money opportunities, or some very smart investors are about to lose a ton of dough. I'm betting on the former.

Brrrrrring! It's related Foolishness calling: