The US Government announced today big changes for all iPhone/iPod/iPad users. Starting from today, Jailbreaking and Unlocking of these devices, along with rooting of Android devices and ripping of DVSs (for educational purposes only) are completely LEGAL into the United States, unless they are violating copyright law.
This is a major hit Apple's face, who, because of its strict policy, didn't let users install unauthorized apps. This decision is a big news for users who were afraid that jailbreaking could bring them into illegality, so, starting from now, they can jailbreak and unlock their iDevices without any fear. However, it is not clear if Apple's policy is still applicable, as they might still refuse to offer support if the device was jailbroken (I'm not sure if this decision puts them into illegality if they continue doing that, we'll most probably get a clarification of this on following period).
You can read more on this subject on Redmond Pie (they've also included the new DMCA legislation).