There are lots of reasons you would jailbreak iphone 4 . The most common reason is to use this awesome phone on networks other than At&t or Verizon (or whatever network provides your iPhone 4 if you aren't in the USA). Besides using your iPhone 4 with other networks (this is commonly referred to as "unlocking" with other phones), you might want to install apps, tweaks, or themes that Apple hasn't approved for one reason or another. Like an austere father, Apple has become notoriously picky about the kinds of things it allows on its "perfect" child, the iPhone. Thus, a "black market," full of any possible app or tweak has flourished. And jailbreaking allows you access to it. 1. Use other networks than the phone was manufactured for Wherever you are in the world, Apple has negotiated contracts to make the iPhone 4 exclusive. It has done this to keep the price high, secure control over use, and maintain an air of exclusivity and superiority for iPhone 4 users. This is quite contrary to most other smart phones, which compete pretty openly against other smart phones and networks. Contrary to many people's beliefs, iPhone 4 is actually the third most used smart phone, behind number one Android, and number two Blackberry. Jailbreaking and unlocking allows iPhone 4 owners to choose their network, which they might do based on price or network coverage wherever they are.