A recent report from AllThingsD stated that from March of this year until now (June), the amount of carriers across the globe that have the iPhone has jumped from 186 to 200 carriers. In light of WWDC this week and the expected release of the iPhone 5, this is a bold step on Apple's part to continue expanding the iPhone worldwide.
Goldman Sachs analyst Bill Shope in the article quotes this reason why Apple is on the move for greater expansion;
Apple is adding lots of new carriers abroad. They’ll more than make up for any decline due to folks holding off on their iPhone 4 purchase for news of the iPhone 5 or 4s.