The booming mobile advertising market grew from $1.4 billion in 2011 to $4.1 billion in 2012, and it’s projected to hit a massive $7.3 billion in 2013. And almost all of it is spent on Apple’s ecosystem. There’s a reason that even though Android has almost caught up to iOS in downloads, it’s still way behind in monetization. Partially, it’s because iTunes has a long and successful history of commercial transactions, so people feel comfortable clicking and shopping and buying on iOS. Partially, it’s because Apple was the leader in mobile for so long. Get the full story at VentureBeat