US mobile ad spending will rise 180% in 2012 to just over $4bn. Pandora will pull in $224.8m for a 5.9% share, reaching $495.6m of mobile advertising revenues in 2014. Google is in first place with $2.2bn of estimated US mobile ad revenues in 2012 for a 56.6% market share. Facebook takes second place with $339.3m / 8.8%, and Twitter fourth with $134.9m / 3.5%. Read more.