Types

• There are two main types of cell phone jailbreaking. The first type (technically known as a vertical jailbreak) allows a user to access features that otherwise would be available only to those with upgraded service or access. The second (technically known as a horizontal jailbreak) enables a user to access the information of other users. This is similar to hacking.
  
  

Rise in Popularity

• With the popularity of the iPhone, jailbreaking has become more widespread because of Apple's exclusive contract with AT&T. Jailbroken iPhones are able to access the iTunes store and download third-party applications.
  
  

Dangers

• Jailbroken phones are often unable to safely access manufactured software. And when the phone is updated, the jailbreak likely will be undone.