Since September 2011, Apple (AAPL 0.07%) has announced fewer than a dozen new wireless carriers selling the iPhone. Currently, the total number of carriers that offer the iPhone stands at about 240. Samsung, on the other hand, has devices on nearly all of the world's 800 carriers. This structural issue could be hurting the iPhone's long-term growth prospects. In this video, Fool contributor Steve Heller and analyst Rex Moore discuss the issue and what Apple could do to expand its addressable market.