1. Mobile first - they take advantage of the unique properties of mobile devices and cannot be fully replicated with a personal computer based service
2. Accomplish tasks on behalf of person or otherwise make life easier
3. Take advantage of more than one hardware feature on device (e.g., camera, gps, accelerometer, microphone)
4. Are not single purpose apps
5. Context aware
Why is all this important? Because of the massive potential for disruption of existing businesses that DON'T take advantage of the unique capabilities of mobile. One of many examples is social networking (yes the mighty Facebook). Due to the legacy of its origins on wired internet computers, Facebook's biggest competitive threats come from services that leverage the contextual information and capabilities unique to mobile devices.