After it became illegal to unlock carrier cell phones thanks to the DMCA, a ton of backlash started up to try and get the laws changed back. After tons of petitioning, a bill finally made its way to the Senate floor, and after a few months of work, it's finally being signed into law. The appropriately titled Unlocking Consumer Choice and Wireless Competition Act makes it perfectly legal for a consumer to unlock their handset once their service contract with their carrier expires, allowing them to take the device to another compatible carrier if they so choose.
Between now and when it became illegal to unlock your device, you could go through the carrier and get them to unlock the device, but if you've ever tried to get a company like AT&T or Verizon to unlock your device for use on another carrier, you've probably noticed they didn't exactly enjoy letting their devices off of their network. With this bill, you'll be able to unlock the device yourself without carrier intervention as long as you're out of your contract.
source: White House
Congress actually passed a bill this year! They must not like their carrier, but like the phone We bought them.