From the Grokster Decision:
Of course, in the absence of other evidence of intent, a court would be unable to find contributory infringement liability merely based on a failure to take affirmative steps to prevent infringement, if the device otherwise was capable of substantial noninfringing uses. Such a holding would tread too close to the Sony safe harbor.
Edward Felton comments on this on the excellent Freedom-to-Tinker weblog. Corante & Ernest Miller have interesting insights, and I need more time to absorb it (Also, last night’s meeting of Houston copynight raised a lot of questions that have addled my head).
Eric Goldman writes about the legality of trackerless bittorrents.