An interesting IGN Gear article lays out the pros and cons of jailbreaking your favorite mobile phone device, and points out that many of the things that were illegal to use before the Library of Congress ruling, remain just as unlawful. Last month the Library of Congress ruled that it was okay to jailbreak a mobile phone under "fair use." This ruling was a response to digital rights advocacy groups, who urged the Library of Congress to make a determination.
The whole point of this decision was to allow users to install legally obtained software on smartphones whose operating systems might otherwise prevent them from so doing (ahem - iPhone, Android, etc.). But a larger appeal might be with those that want to copy copyrighted materials - aps, music, moves, etc. - to phones. As the article points out, this is still very illegal.
The article goes on to explain why jailbreaking your phone might be a bad idea for you: some examples include voiding your warranty, generally effing up your phone, no more technical support from your phone maker, etc. Then there are the potential benefits like being able to run an app that the overlords at Apple or Google have not "authorized," having the ability to develop and deploy apps for your phone, and unlocking extra features on your phone not possible due to rigid nature of operating systems.
It's a pretty decent article and at the very least gives readers a glimpse into what all this jailbreaking business is about.. Check it out at IGN Gear.