Technomaly

There are numerous of advantages of jailbreaking an iPhone. But to name a few of the functions that jailbreaking can offers are:

1. tethering
2. multi-format video playback
3. turn by turn talking GPS navigation
4. Bluetooth file transfers
5. power management
6. Voip over 3G
7. instant messenger in the background
8. brighter flashlight
9. customized menus
10. Unlock and use any GSM carrier

For everyone else, these types of features are somewhat expected in modern devices, and if not they tend to jailbreak it.