Last year, according to the IAB, mobile ad revenues came in just under $3.4 billion in the US. On a global basis eMarketer (aggregating a range of third party data) estimates that mobile advertising was worth $8.8 billion. Of that Google was responsible for a staggering 52%.
In 2013 eMarketer argues that Google's share of global mobile advertising will continue to grow to 56%.
Impressively or shockingly, nearly 66% of global mobile ad revenue in 2012 was concentrated in the top five companies according to eMarketer. In 2013 that figure is expected to exceed 75%.
The eMarketer forecast is that this year mobile advertising will be worth nearly $16 billion worldwide. In other words, roughly $12 billion of the world's mobile ad revenue will be concentrated in the top five US-based companies -- and most of that at Google.
By comparison, the top 10 PC-based online advertising companies in the US control 72% of the revenue, while the top 50 control nearly 90%.
The eMarketer numbers may well be off. For example their YP figures are incorrect and underestimate the company's mobile revenues for 2012. However directionally the numbers are accurate and indicate the "concentration of mobile weath" in a small number of companies -- as well as the dominance of Google as the world's largest mobile ad company. (In terms of total digital advertising globally, Google controls 33%.)
Facebook is really the only other player currently in a position to challenge Google for mobile ad revenue and reach.