A wireless network is considerably different to a fixed-wire network. The bandwidth of the network is typically much smaller, at least at this point in time. Reliability profiles are considerably different, particularly where users move in and out of coverage areas, disappear into tunnels, and so on. Latency may also be an issue in wireless networks. An additional factor is that there are a number of mobile network standards in place across the world, and they do not interoperate seamlessly.
Some countries even have incompatible standards in different regions.
Finally, it is important to realize that the market is different where wireless applications are concerned. The types of applications that are suitable for use on mobile devices are not the same as those that are popular on fixed-wire environments. Typical users of mobile applications are likely to be a broader subset of the population than PC users. Even the context in which the applications are going to be used will be different. This highlights the most important aspect of mobile application design, which is to make the application easy to use in the context, and on the device that it will be accessed from.