Can free speech cause a tragedy of the commons? In other words, can there be too much speech?
In the original parable of "The Tragedy of the Commons", each villager has the right to keep as many sheep as he wants on the commons shared by the village, and each has an incentive to add at least one more sheep. If everyone acts accordingly, the commons will be ruined. The author, Garrett Hardin, later said that he should have titled his work, "The Tragedy of the Unregulated Commons".
Users of Usenet and unmoderated mailing lists experience a phenomenon which feels like a tragedy of the commons. Someone shriller and angrier than the average user begins posting an endless series of intemperate rants; soon more reasonable users unsubscribe from the group and the "polluter" is left alone.
Is this really a tragedy of the commons? A public mailing list certainly feels like a "commons", available to everyone. If it is not policed by a list moderator, every user is free to add one more comment--one more insulting or intemperate posting--polluting the virtual commons as surely as the sheep pollute the real one.
The analogy breaks down when we examine the list phenomenon more closely. A list is "push" technology: once you subscribe, all the messages arrive automatically; you do not do anything more to select or request them. The inevitable death of an open mailing list is dictated by the fact that you are purchasing a package of things-- messages--which arrive together. Since anyone is free to include a poison message in the lot, at some point the content of the entire list will lose interest, the good content outweighed by the bad.
But whatever tragedy is experienced in the death of a mailing list bears no relationship to speech delivered via "pull" technology--in a bookstore or on the World Wide Web. As long as the speech I want is available and I am free not to select the speech I don't, there can be no tragedy of the commons. The existence of a disfavored sheep somewhere is not a tragedy of the commons unless its consequences are the wrongful death of my sheep. In a world where speech is delivered via "pull", my sheep and yours can co-exist.
If a Usenet mailing list is a commons, it is only by virtue of the peculiarity of its technological means of delivery as an indivisible object. (I am oversimplifying and ignoring the possible application of filters or killfiles to exclude the speech I don't want.) However, a list lacks something which most commonly understood "commons" share: necessity. There may be only one green outside town on which to graze your sheep, but there are a myriad mailing lists, and this one is being pushed at you only because you requested it. If you're not happy with it, choose another, or start your own. Similarly, the collection of all Usenet mailing lists is not a commons, because you are not required to subscribe to any other list and nothing that happens on another list can affect yours. Similarly, seen vaguely from a distance, the set of all movies playing in my city may seem to be a commons. You may complain of the predominance of Hollywood action adventures. Nevertheless, movies are a pull technology, and you may choose to see only the most literary foreign films shown in revival houses.
Looked at this way, a commons is something pushed upon us and which we do not have the option to reject. The air we breathe is a commons, but the airwaves are not, as we decide whether to have a television in the house and choose the programs we watch.
Under this approach, no medium of communications is a commons with the possible exception of certain verbal and visual speech in public places. Books, movies, web pages are not push technology. Television programming and Usenet email are pushed at us only as the result of a choice we made.
This "push/choice" analysis justifies very limited speech regulation, of a type that has already been found valid under the First Amendment: reasonable time, place and manner restrictions of bullhorns, public speaking and billboards, all of which are unavoidable push technology in public places.