To say that Facebook's mobile ad revenue growth has been impressive is an understatement. It has been, what you might call, meteoric.
In the course of a 12 month period the company has gone from less than 10% of ad revenue from mobile to 41% in Q2 of this year. By the end of this year (or very early next) 50% of Facebook's ad revenue will likely come from mobile. (By comparison, in 2012 more than half of Twitter's ad revenues came from mobile.)
In Q2 '13 Facebook made more than $650 million in mobile ad revenue. If current trends continue expect Facebook to have a $1 billion mobile quarter by 1H 2014 (and possibly Q1 earnings). That would enable the company to claim a $4 billion annual mobile-ad revenue run rate.
Based on averages and simple math, Facebook made roughly $0.80 per mobile user in Q2 on a global basis -- up from $0.50 in Q1 of this year. However developed markets offer more revenue than emerging markets and so the revenue generated per mobile user will vary considerably from market to market in practice.
In 2010 we asked "How Long Before Facebook is a Mobile Ad Network?" and predicted that when Facebook turned on mobile ads it would immediately become the largest mobile "network."
As formidable as Facebook is becoming in mobile Google is still dominant globally. Incredibly, Mountain View is expected to capture more than 50% of mobile revenues on a global basis this year. Facebook claims a much smaller percentage of mobile revenues, but still ranks as the number two player in mobile advertising today.