fun facts for you: Mobile games will take in more than $11 billion in revenue by 2015. That's about equal to the current take from console software, mind you. Given that console software sales have been shrinking for the last several years, rather than growing, it seems reasonable that mobile game revenues will overtake console games in the not too distant future. (Which kind of makes Activision's strategy of avoiding mobile and social games hard to figure out.)
More data: the majority of the revenue will be from in-app purchases. Though I wonder if advertising won't be close... it's going to be interesting to see how Android revenue numbers change as in-app purchasing takes hold in that market.
The real key to understanding all of this is that discoverability is still a problem. No, it's going to get much, much worse. Marketing gets tougher as time goes on in these crowded markets. We can hope that trusted sources will appear over time that can command a huge following (and thus become a prime place for marketers to advertise or promote), but so far that hasn't happened.