First, it's a bit ironic that the iPhone is the center of mobile payments in the US when it's Japan release was marred by many Japanese pundits declaring the iPhone would fail in Japan because it lacked integrated mobile payment systems such as the popular SUICA chip (which you can charge with cash or link to a credit card and use for “touch” payments at train stations, convenience stores, restaurants, and so on). It's often argued that the iPhone has taken off in Japan because of its excellent web browser, usability, and utility as a “second phone” to accompany your old phone with standard Japanese features like TV and high res camera.

Second, carriers like ATT & Verizon could look to DoCoMo, KDDI, and Softbank (Japan's top 3) for ways they could profit from facilitating this market. It's my understanding that mobile service providers in Japan typically charge less than 10% commissions for the benefit of reaching vast audiences and integrated billing, which combined with years of Flash friendly phones have led to a strong mobile gaming infrastructure, whereas the US counterparts charge much more.