刚刚在reddit上看到的，附上原文网址:
https://support.apple.com/en-us/HT201954
Title: Unauthorized modification of iOS can cause security vulnerabilities,
instability, shortened battery life, and other issues
This article is about adverse issues experienced by customers who have made
unauthorized modifications to iOS (this hacking process is often called
"jailbreaking").
iOS is designed to be reliable and secure from the moment you turn on your
device. Built-in security features protect against malware and viruses and
help to secure access to personal information and corporate data.
Unauthorized modifications to iOS (also known as "jailbreaking") bypass
security features and can cause numerous issues to the hacked iPhone, iPad,
or iPod touch, including:
Security vulnerabilities: Jailbreaking your device eliminates security layers
designed to protect your personal information and your iOS device. With this
security removed from your iOS device, hackers may steal your personal
information, damage your device, attack your network, or introduce malware,
spyware, or viruses.
Instability: Frequent and unexpected crashes of the device, crashes, and
freezes of built-in apps and third-party apps, and loss of data.
Shortened battery life: The hacked software has caused an accelerated battery
drain that shortens the operation of an iPhone, iPad, or iPod touch on a
single battery charge.
Unreliable voice and data: Dropped calls, slow, or unreliable data
connections, and delayed or inaccurate location data.
Disruption of services: Services such as iCloud, iMessage, FaceTime, Apple
Pay, Visual Voicemail, Weather, and Stocks, have been disrupted or no longer
work on the device. Additionally, third-party apps that use the Apple Push
Notification Service have had difficulty receiving notifications or received
notifications that were intended for a different hacked device. Other
push-based services such as iCloud and Exchange have experienced problems
synchronizing data with their respective servers.
Inability to apply future software updates: Some unauthorized modifications
have caused damage to iOS that is not repairable. This can result in the
hacked iPhone, iPad, or iPod touch becoming permanently inoperable when a
future Apple-supplied iOS update is installed.
Apple strongly cautions against installing any software that hacks iOS. It is
also important to note that unauthorized modification of iOS is a violation
of the iOS end-user software license agreement and because of this, Apple may
deny service for an iPhone, iPad, or iPod touch that has installed any
unauthorized software.
简单来说，就是指任何对iOS装置进行未经授权的修改行为(也就是越狱)，
会造成装置的安全性下降，导致恶意程式可能借此入侵装置。
并且有些软件的使用可能会使iOS装置变得更加耗电，
还有可能导致一些正常的App的运作出现错误或是闪退等现象
进行严重的修改的话还可能会造成iOS出现无法修复的错误，
并在进行系统更新时使装置无法使用。(淦哪个白痴在越狱后还会升级啦)
最后，说是越狱违反了iOS的使用者同意条款，Apple有权拒绝服务
任何有安装未经授权软件的装置。
虽然很想吐槽苹果竟然敢说自己系统很稳定，不知道是哪来的自信
但他说的其实也没错啦。越狱本来就要自己承担各种风险。
如果今天装置真的是因为越狱而导致损坏，他们也没必要进行负责。
就像Android现在很多厂商也是只要root就得先解锁Bootloader，
解锁Bootloader的话装置就会破保。
只能说我还是会继续越狱下去，但是要提醒大家要小心，
不要在越狱之后就在Cydia装盗版软件，或是跑去乱超频什么的。
因为已经取得装置的最高权限了，做什么都要谨慎。