In the modern era mobile devices are becoming ubiquitous, even to the less technologically adept. The popularity of Apple's iPhone has secured smart phones as "the future" and other digital devices (PDA's, hand held games consoles, Sat Nav) are expanding in functionality.
A large number of these devices use custom operating systems and software that is not compatible with "normal" computer forensics software. On top of that they employ any number of proprietary physical connector, data storage and encryption standards. The result is that computer forensics tools and methodology is simply not effective against such devices.
This has led to the development of the field of mobile device forensics.