Unlocking your cell phone will soon be illegal in the U.S.
Freeing your phone from its carrier chains will be a violation of the law
On January 26, the cell phone or smartphone you buy from your carrier will no longer be yours to mess with. In short, one can argue that it really won't be yours at all, because unlocking the device--freeing it from carrier restrictions, allowing you to use the phone on other carriers around the world--will be illegal.
According to Mashable:
In October 2012, the Librarian of Congress, who determines exemptions to a strict anti-hacking law called the Digital Millennium Copyright Act (DMCA), decided that unlocking cellphones would no longer be allowed. But the librarian provided a 90-day window during which people could still buy a phone and unlock it. That window closes on Jan. 26.
Fortunately, you can still buy devices at full retail price that are already unlocked, like the iPhone 5 or Google's Nexus 4, which sells at $300 or $350 depending on which version you buy (both of which are great deals for sophisticated and unlocked devices).
Otherwise, you can't just buy a smartphone on AT&T with a contract, for example, then decide two months later you're just going to unlock it and bring it to T-Mobile. Technically, you could do just that, but you'd be breaking the law.
In order to unlock your phone within the confines of the law, at least as of January 26, you'll have to get your carrier to do it for you once you are no longer under contract. So if you plan on doing this on your own, you'd better hurry up because you only have to days left to do this legally!