With the pace of growth in the mobile ad space, it is likely that whoever dominates that space will dominate the digital space overall.
eMarketer has done some research taking a look at the mobile Internet and overall digital space and which companies are in control.
It is probably not much of a surprise to learn that Google is the true 800 (or is it 900?) lb. gorilla in the market. Based on the findings, most other companies, aside from Facebook and Amazon to some degree, are looking like their growth is going to be hard to come by.
First, here is a look at the mobile Internet ad market share.