There were other signs that Apple might begin lifting restrictions on previously forbidden application categories. Yet it took a very public investigation by the FCC following Apple's hobbling of Skype and rejection of Google Voice for the iPhone to persuade Apple and AT&T to relent on VoIP telephony. And though apps such as Google Voice and Skype can now be used on the device, limitations still abound. Internet tethering, an intensely desired feature, is one high-profile example. Built into OS 3.0, the capability remains restricted in the United States by monopoly iPhone carrier AT&T.
Meanwhile, Apple has not altered its SDK restriction on interpreted code, which rules out Flash and Java applications (although Adobe purportedly has a Flash work-around), as well as Flash video playing inside the iPhone's Safari Web browser. Web browsers themselves remain off limits as an app category, except for simple repackaging of the iPhone's built-in Webkit HTML rendering engine.
Then there are certain iPhone capabilities that Apple still reserves for itself: background processing, video recording on pre-3G S devices, application launching, video output, lockscreen and wallpaper customization, interface skinning, GPS tracking, and remote control of an iPhone from your desktop computer (a la Apple's Mac OS X Screen Sharing).
Each of these limitations provides incentive for the jailbreaking community to thrive.
Apple's ongoing objections to iPhone jailbreaking
Apple's company line on the kind of features jailbreakers seek remains steadfast: These features reduce battery life, slow performance, introduce security vulnerabilities, stress the 3G network, and increase Apple support costs. It is under the auspices of these objections that Apple routinely blocks apps it doesn't like from its App Store. Some developers argue, however, that often such blocking happens more for competitive reasons than out of concern for iPhone users' safety and productivity.
Still, many of Apple's concerns have in fact materialized in jailbroken apps. Background processing does reduce battery life and overall performance, according to users, but these same consumers say the feature is worth the hit as long as they can control its application. Battery drain is also a key symptom of a particular jailbroken-iPhone worm infection. Jailbreaking proponents, however, point out that the worm can only infect phones that users haven't properly secured by changing the default password. As for stressing the 3G network, most signs point to regional differences in AT&T cellular data capacity as the root cause of this issue, as opposed to anything that jailbreaking would exacerbate.