The DMCA, if you haven't heard already, is a broad and massively restrictive law, that makes it a criminal offense to produce or share technologies that can be used to circumvent copyright measures. Measures like the DRM. While there is nothing wrong in that noble endeavor, the draconian powers invested in, and the broad applicability of the law make it particularly distasteful.
The DMCA is behind the now infamous Cease and Desist take-down notices, that websites regularly have to content with. The DMCA has made it very easy to send out these C&D letters, independent of actual misconduct or potential litigation. Chilling Effects, is a major site, that catalogs some of these C&D letters.
Now in all the disaster that DMCA is, there is a tiny ray of hope. Every three years, the Library of Congress is entrusted with the job of reviewing feedback to the law, and identify uses for circumventing copyright, that has legitimacy. In other words, the LoC makes certain acts of DRM cracking legal. Which of course is valid only for the next three years before it come due for further review.
Today, the Library of Congress issued its latest on “Exemptions from Prohibition on Circumvention of Technological Measures that Control Access to Copyrighted Works”. The big surprise was the rule allowing the removal of DRM to use mobile phones with different carriers - a.k.a legitimizing the jailbreaking of the iPhone. Of course this in no way prevents Apple and carriers from locking/crippling the phone in the first place. Nor does it need Apple to continue to support a jailbroken phone. But if you did need to use the iPhone differently from how Jobs would approve - at least you sleep well at night knowing that the police will not be breaking your door down.