What does it mean to jailbreak an iPhone?
At one time or another, many people with Apple iOS-based devices, such as the iPhone, iPad or iPod touch, have looked into "jailbreaking" them. Jailbreaking means bypassing the restrictions Apple puts on the operating system and taking full control of the device.
Should you jailbreak your iPhone to get iOS4?
Sure, your old first-gen iPhone may not have the horsepower to run iOS4, but you can hack it to kick your shiny, new, legit model's ass in terms of reception: Use it as a Wi-Fi-only landline. Because a jailbroken iPhone can run apps in the background, you can keep a VoIP app and Google Voice up and running at all times.
What are the pros and cons of jailbreaking an iPhone?
Pro: Access the iOS file system. Jailbreaking exposes the inner workings of an iPhone, iPad or iPod Touch to its user, which can be very useful. For example, installing a secure shell (SSH) client lets you securely move data between two devices on a network.
What can you do with a jailbroken iPhone?
If your device is jailbroken, you can install apps that aren't available from the iTunes App Store. For example, Cydia is a framework that lets you add other unauthorized apps, such as games and networking tools. "Apple is fairly restrictive.