EFF clarifies somewhat legality of unlocking and jailbreaking in the U.S. | 9to5Mac.

I see many iPhone unlock services on the web. What method do you use to accomplish this?

Our method itself is confidential, but we take pride in the fact that instead going the ‘cheap’ route like some of our competitors (such as illegally buying access to hacked cell carrier logins!) which are sketchy and easily traceable (risking re-lock of your phone), our method gets the IMEI of your iPhone into the database of your carrier (as well as Apple) in a legitimate and secure way.

Here:  www.chronicunlocks.com