The effectiveness of mobile advertising is still being debated, but media buyers are already going all-in while also increasing their presence on the Web.Mobile ad spending grew 180 percent to top $4 billion in 2012, according to the latest estimates from digital marketing research firm eMarketer. At the same time, the Interactive Advertising Bureau and PwC US report Internet ad revenues totaled $9.3 billion for the third quarter.See Also: AAM Data: Mobile and Digital Monetization Expected to Rise On the mobile side, eMarketer highlights this year’s exponential growth as an outlier–the expected growth rate for 2013 is a comparatively meager 77 percent, and it slows from there–but predicts the market will surpass $20 billion by 2016.Google is still the mobile-ad king with more than $2.1 billion in revenue and 57 percent market share, but others are closing the gap.Facebook–who only began offering mobile-specific advertising via “Sponsored Stories” mid-way through this year–was the second-largest seller with an expected haul of $339 million for 2012. Mobile earnings estimates for the social giant were as low as $45 million earlier this year. Facebook had no reported mobile ad earnings in 2011.Twitter, also showing no mobile ad revenue in 2011, was this year’s fourth-largest earner with $135 million.Internet Ad Revenues Grow 18 Percent in Q3While mobile was exploding, Internet ad spending continued its steady climb through the third quarter.The sector grew 18 percent year-over-year and 6 percent from the second quarter to reach $9.3 billion.”Sustained growth in internet ad revenue despite economic head winds is a testament to the value marketers get from using digital media,” says Sherrill Mane, SVP of research, analytics and measurement for IAB, in a statement. To stay updated on the latest FOLIO: news, become a Facebook fan and follow us on Twitter!