"In response to similar lawsuits, Verizon and Sprint, both CDMA carriers, have agreed to provide the software code to unlock cellphones after customers nationwide have completed their original contract, attorneys said. "That was the compromise we ended up with to get the cases settled," said California attorney Robert Bramson, one of the lawyers suing carriers T-Mobile and AT&T.
T-Mobile and AT&T fought the lawsuit all the way to the nation's high court. The two carriers, on the GSM network, are accused of unfair business practices by locking down their phones to their service plans. Last year, Librarian of Congress James H. Billington listed cell phone unlocking as one of six new exemptions to the Digital Millennium Copyright Act, or DMCA."
So locking handsets seems to be something consumers are strongly against, especially since unlocking them isn't illegal (in the US) - http://blog.wired.com/27bstroke6/2006/11/unlocking_cellp.html.