Big negative: the jailbreak/unlock world of iPhones is very much like the wild and crazy earlier days with (mostly Windows) software in the 80s and 90s. There are countless versions of an equally cryptic variety of software packages and types (“pwnage”, “redsn0w”, “cydia”, ad nauseum), all of them very poorly documented by hacker types with vague monikers and shadowy backgrounds (Russia? Slovenia? China?). Some of these software packages co-exist, others are downright dangerous when mixed. Again, all of this is very poorly documented, so you have to make your way around at your own risk
Who do you trust: When you jailbreak an iOS device using a tool such as the jailbreakme site or one of the tools offered by the iPhone Dev Team, you don’t really know what’s happening to your device. At the end of the jailbreak you should have a more open iPhone, iPod touch, or iPad and a copy of the Cydia app. But what else has gone on in the background?
Up to this point, nothing, it seems. I’ve jailbroken iPhones and iPod touches for years and I’ve yet to have a problem where my data was exploited. But, as they say in the questionable-investment business, past performance is no guarantee of future results. It’s possible that a jailbreak will come along (though not likely from the iPhone Dev Team) that does The Bad Thing.
Your phone is more open to attack: When you jailbreak your device and enable SSH, its more accessible from the outside than it once was. Far too many people jailbreak their phones (or purchase jailbroken and unlocked phones) without then changing its default “alpine” password. And some of those people have suffered in the form of baddies breaking into their devices.
If you’re going to jailbreak your iPhone, do your future self the very big favor of changing its password. Cydia’s home screen provides a Root Password How-To button. Tap it to learn how to change the device’s password.
Your battery life could suffer: Some third-party apps and processes care very little about how much power they pull from your iOS device. If you’re running some of these things on your iPhone, iPod touch, or iPad, your battery could drain in short order.
Your phone could become less stable: Say what you will about the sometimes-quirky nature of the App Store’s approval process, at least apps have been vetted—hopefully to the point where they shouldn’t take down the entire device when they crash. There’s no guarantee that apps offered via Cydia will be as stable.
Your warranty: In a recently released KnowledgeBase article—which outlines the risks of jailbreaking an iOS device—Apple states:
“It is also important to note that unauthorized modification of the iOS is a violation of the iPhone end-user license agreement and because of this, Apple may deny service for an iPhone, iPad, or iPod touch that has installed any unauthorized software.”
If something goes wrong, there is a chance that it can be fixed, but there is a chance of your iPhone becoming bricked, or inoperable.
Apple does not like jailbreaking.You need to be careful about what you install.
Anecdotal evidence suggests that if you walk into an Apple Store with a misbehaving and jailbroken iPhone in the hope of getting some help with it, you’ll be politely turned away. In most cases, you can return your jailbroken iPhone to its original condition simply by restoring it in iTunes, thus leaving no evidence. However, this presents an ethical issue. You did something to the iPhone that broke your warranty. You should therefore not expect support for it.
Updates and jailbreaks: Apple hasn’t gone out of its way to issue updates that intentionally damage jailbroken iPhones. (These updates certainly undo jailbreaks, but they haven’t permanently damaged iOS devices—though one update did put jailbroken 2G iPhones out of commission until a subsequent jailbreak became available weeks later). Given the company’s history of largely turning a blind eye to jailbreaking and the added ruling that jailbreaking and unlocking are legal, it’s highly doubtful that Apple will take any deliberate action to decommission jailbroken phones.
At the same time, Apple’s just as unlikely to spend much time thinking about the effect an update may have on jailbroken iOS devices. It’s possible that an update will come along that does threaten a jailbroken or unlocked iOS device. And that means that those with these jailbroken devices must be vigilant about how and when they update their gear. They will certainly want to hear about the experiences of others before updating, as well as possibly wait for a jailbreak or unlock that’s compatible with that update.