ve always been key in the competition. The rapid decline of the voice service price greatly increased the usage of mobile calls. However, the well-developed voice services and relatively high prices of data services have restricted the growth of data service usage. Currently in the U.S. mobile services market, mobile service for business activities such as e-commerce and internet busi- ness are more developed as an auxiliary service [12]. The U.S. MNOs commonly take a walled-garden strategy, dominating the value chain with the control of the provision ofhandsets, contents, and applications. Comparative Study on the Mobile Data Service Development MNOs sell low-price locked handsets to customers together with a mobile service contract and customers generally have to pay the early termination fee if they choose to terminate the services before the end of the minimum term. Meanwhile, they keep tight control on what applications are available and what services consumers can access on handsets by selling content through their own branded portals. The Apple iPhone launched by AT&T in June 2007 represents a funda- mental change in this walled-garden business model. However, Apple has itself also created a walled garden on the iPhone in terms of branding and applications and the exclusive agreement between Apple and AT&T makes iPhone unavailable for subscribers of any other SPs. The providers have begun selectively to allow third-party CPs to market the multimedia content directly to their subscribers. However, the walled-garden business model still dominates the mobile data service operation [4]. Those strategies are largely shaped by the tough competition. The strategies of incompatible technologies and services, high subsidy on handsets, and exclusive access to contents and applications increase the switching costs of consumers and accordingly help to retain customers. In addition, the pressure of competition makes the providers cautious to promote new services which usually go with high risks. The walled-garden strat