Say screen name "John Doe" was subpoened for comments he made on FreeRepublic. There is no proof that he did or did not type the words. Nobody can prove. John Doe can say he left his computer on, and he had nine people in his house.At which point, the case against John Doe for defamation will end, and a new case against John Doe for tortuously gross negligence will begin--and John Doe's testimony will be the sole exhibit needed to get a verdict against him.