Thanks in large part to the Apple iPhone, the mobile videogame industry is booming in the U.S. That’s good news for the mobile game publishers who are now working with Apple iPad to bring even more innovation to future games starting in late March. According to a new study from SNL Kagan, “Economics of Mobile Games,” mobile game publishers grossed nearly $540 million in top-line revenue in the U.S. in 2009, up at a 12% from $382 million in 2006.