Over at Ars Nate Anderson makes an important point that hadn’t occurred to me: The cell phone unlocking exception I mentioned in my last post applies only to the act of circumvention, not to trafficking in circumvention devices. That means that you’re safe if you unlock your own iPhone, but if you develop software or hardware to help others do so, you could wind up in legal hot water under the DMCA.
Of course, that depends on whether unlocking your cell phone is an act of circumvention in the first place. It’s not obvious that cell phone locks “effectively controls access” to a copyrighted work. Perhaps AT&T could argue that unlocking your phone is the first step toward pirating ringtones, but it should be possible to develop a hacking tool that enables carrier-switching without enabling ring-tone piracy.
In any event, this is almost certainly not the sort of situation Congress had in mind when they passed the DMCA.