It?s not been long since it was made legal in the US to unlock/jailbreak the iPhone and other mobile devices. Only for the purpose of switching carriers of course. The developers behind the most popular jailbreak method, Ultrasn0w, are  most likely relieved about this.

They are now able to legally distribute their application without worrying about facing a law suit. And have now released an updated version of their tool for the iPhone 4.

Jailbreaking frees the iPhone from the restrictions of Apple?s default settings, allowing users to install custom software from sites other than the iTunes App Store. The practice has proved popular amongst technology enthusiasts, and will allow you to use other carriers. so in the Us that means users aren?t tied down to AT&T.