Disadvantages? Risks of Jailbreaking?
Jailbreaking is awesome but there are some disadvantages to it.
Bricking
The term suggests a software error that rendered the device completely unrecoverable without some hardware replacement. Now with regards to iOS devices, I feel that this is a rather loose term. In my experience, I haven't heard of a device that has been legitimately bricked. A device that was deemed to be bricked can be recovered through DFU mode and iTunes restore. If there is indeed a chance for bricking, the percentage is very, very low.
Warranty Void
Jailbreaking is a perfectly legal act but the folks over at Cupertino thinks otherwise. Any attempt to jailbreak an iDevice will void your warranty. So with that said, Apple has the right to deny you with any service repairs in case your device is damaged or malfunctions. So just a little tip: you might want to restore your device prior to taking it to Apple for repairs since they won't be able to detect it.
Bugs and Glitches
While the iOS is a fairly bug-free experience, the same doesn't apply to jailbroken devices. Jailbreaking itself will make your device less stable. So you will experience issues like some apps will crash or stop working altogether, faster battery consumption, noticeable slowdowns, freezing, loss of data and other errors. Simply put, don't expect your device to work as smooth and stable as a non-jailbroken device.
iOS updates will break the jailbreak
Apple and the jailbreaking community is on a continuous cat and mouse game. If a certain firmware version has been jailbroken, you can trust that the exploit will be plugged in the next update. If you update, you will surely lose your jailbreak and all your jailbreak tweaks and apps will stop working. As a rule of thumb for jailbreakers, do not ever update your firmware version unless there is an available jailbreak solution for it.
May Compromise Security
The iOS's closed nature enables it to be one of the most secure mobile OS available. While jailbreaking does open your device for a new world of possibilities, it does render it susceptible to malicious content such as viruses and malware that can steal personal information or damage your device.