In United States of America vs William Lawrence Cassidy, in which Cassidy was accused of harassing a Buddhist religious leader via Twitter, the judge drew a fascinating distinction b/w public speech on Twitter and blogs on the one hand, and speech "specifically addressed to and directed at another person" such as email (and Twitter DM's one presumes?). The distinction was based on an analogy to the communications media available at the time that the Bill of Rights was written.
The judge said that a blog, or a micro-blog, was like a bulletin board that a colonist might have planted in their front yard: “If one colonist wants to see what is on another’s bulletin board, he would need to walk over to his neighbor’s yard and look at what is posted, or hire someone else to do so.”
Twitter, according to the analogy, would be like having news from one colonist’s bulletin board automatically show up on another’s. The key is that the second colonist could choose to “[turn] on or off" such a feature on his bulletin board. “This is in sharp contrast to a telephone call, letter or e-mail specifically addressed to and directed at another person,” he concluded.
I love these kinds of historical analogies to existing technology. Basic human needs hardly change over time, so every new technology should have a functional analog from an end-consumer perspective.
In this case however I think the judge's analogy is flawed. Twitter is designed for @ replies to indeed be addressed and directed at another person, despite also being public. The analogy would be something like writing an open letter in the newspaper harassing the victim, shouting at her in the town square in a voice loud enough for all to hear, or perhaps writing her a letter and distributing it to the public on a leaflet in addition to giving her a copy. I'm not a legal scholar, so have no idea what the legality of this would be.
The story was reported by the New York Times here.