Facebook Eats Away At Google's Share Of Mobile Ad Pie

Mobile advertising is swiftly becoming a two-horse race. According to the latest eMarketer forecast, mobile ad spending worldwide grew by 105% in 2013 and is on pace to expand to $31.5 billion in 2014.

And the two Internet giants, Google and Facebook, are increasingly taking the lion's share -- the pair netted 67% of mobile ad revenues in 2013, up from 58% in 2012.

The current report marks yet another adjustment from the research firm, as mobile ad dollars balloon far faster than expected. The final spending figure of $18 billion is nearly double the firm's estimates from just four months ago. Much of the tweaking is due to Facebook, whose share of net revenues more than tripled, to 18%, in 2013, only its second year in the mobile ad business.