Among tech circles, it is increasingly common to jailbreak Apple iPhones. "Jailbreaking", or "rooting" the phone, allows the user root access to the filesystem. Apple does not, by default, allow root access to the filesystem, so jailbreaking iPhones allows users to make changes to their iPhones that are not necessarily condoned by Apple.
Jailbreaking iPhones voids the warranty (yes, Apple can tell whether or not your iPhone has been jailbroken). Nonetheless, may people still do it. Is it worth it? Or is invalidating your warranty an unnecessary risk, given the benefits you attain by jailbreaking your phone?
Reasons For Jailbreaking
Users originally began jailbreaking their phones back in 2007, when Apple did not allow third-party apps. They had not yet released the iPhone Standard Developer Toolkit (SDK), but users who wanted to use third-party Cocoa/Objective-C applications discovered how to obtain root access to the file system. This way, users could install third party apps (the most popular category of third-party apps in 2007 was Twitter apps, as there was no native way to tweet from the iPhone without the App store's thirt party apps).
Apple famously locks down its devices. The company's approach to its app store has been called "the walled garden" by critics and fans alike. Apple's approach is simple: if it's not approved for sale or download in the App store, you can't add it to your phone.
While this is fine for most users, and in fact has some security benefits (namely, you cannot add a virus to your iPhone via your app store), some users want their iPhones to do things that Apple does not allow. For example, iPhone announced Wi-Fi syncing at WWDC. Many users with jailbroken iPhones yawned, as they have been able to sync their iPhones over Wi-Fi for over a year. Tethering your iPhone to a computer to use Internet on-the-go? Same deal. The users who had jailbroken their iPhones had been tethering their iPhones for years.
For users who want to push the boundaries of what the iPhone can do, jailbreaking the iPhone may be worth it.
Reasons Against Jailbreaking
The primary reason against jailbreaking an iPhone is that it invalidates your warranty. Is it really worth downloading apps that access private APIs to know that you can't go to the Apple Store for free service? Maybe. However, for most users, this is a difficult decision to justify. In addition, jailbreaking is not guaranteed to work. You could "brick" your phone – that is, render your phone totally useless.
Yes, many of the applications that are available on the Cydia app store (the primary jailbroken-iPhone app store) are useful. However, are they useful enough to justify invalidating your warranty? Probably not.
Unless you *absolutely* know what you are doing, and are comfortable with the risk level involved in invalidating your warranty, you should not jailbreak your phone. If, however, you decide to do so, make sure you know the risks and, if possible, ask someone who has done it before.
(Note: Jailbreaking, according to a 2010 Supreme Court decision, is legal, much to Apple's dismay. They cannot prevent you from doing what you wish with your own device).