• by Laurie Sullivan  @lauriesullivan, December 7, 2011

Brands will spend 12.6% more this year, compared with last, to advertise across the Internet, according to ZenithOptimedia, a Publicis Groupe company. Driven, in part, by online video and accompanying ads, the study shows 16.4% growth in 2012, followed by 17.3% in 2013, and 17.2% in 2014.

ZenithOptimedia estimates paid search will grow 15% in 2012 and 2013, followed by 13% in 2014. The company expects growth to slow as the search landscape matures. Google and Microsoft will continue to focus on ad units and targeting techniques through desktop, mobile and tablet search.

Some of the boost to online ad spending will come from political ads. Republican Tim Pawlenty disclosed his 2012 presidential aspirations on Facebook, while Mitt Romney did it in a tweet. President Barack Obama kicked off his reelection with a digital video emailed to 13 million backers.

The ZenithOptimedia report puts placing a promoted trend on Twitter now costs $120,000 daily, up from between $25,000 and $30,000 when Twitter first launched in April 2010. Now brands will have an opportunity to place ads using a self-serve platform, which the study suggests could drive up prices not only for Twitter ads, but Google paid search ads, as well.

Overall, brands will spend nearly $50 billion on online ads in the U.S. by 2015. Of the formats in this category, online video ads will continue to experience the fastest growth, with an increase of more than 52% this year.

It is no surprise that mobile marketing, supported by ubiquitous apps, advanced browsers and faster speeds, continues to fuel the uptick in dollars. Smartphone ownership now comprises 28% of all mobile phone ownership, with nearly 1 million smartphones activated daily. The average number of ads shown per app is 4.3, and the average session lasts just more than four minutes.

The study also notes that the average smartphone user now spend more time in mobile apps per day than the average Internet user spends online.