Facebook's late push into mobile advertising is paying off big time. A little more than a year after Facebook began serving ads to mobile users, the social network is already the second largest player in the quickly growing market. eMarketer expects Facebook to rake in 15 percent of the mobile ad total this year, trailing only Google which accounts for more than half of mobile ad revenue.

eMarketer's data shows how heavily concentrated the mobile ad market is. The Top 5 ad publishers account for three quarters of the global total and, perhaps even more impressively, Google and Facebook alone are expected to pocket 7 out of 10 dollars spent on mobile advertising this year. Facebook's strong mobile performance has helped the company to recover from the IPO disaster as it helped brush away doubts about the company's potential for growth.