The Supreme Court, in a unanimous decision this morning, ruled that "One who distributes a device with the object of promoting its use to infringe copyright ... is liable for the resulting acts of infringement by third parties using the device, regardless of the device's lawful uses." The case has been sent back to the lower court that ruled in favor of MGM in the first place for trial.
Here's some other resources on the case:
As the EFF piece states, the P2P genie is already out of the bottle. This decision won't put it back in.