inverse rights corresponding to freedom of speech

The issue of free speech (which has been in the news a lot lately) necessarily generates a parallel discussion of rights: To what extent do people have the right to not be exposed to speech? And to what extent should and can people have those rights? In the United States, it's obvious we don't take a binary position on this topic. There is content that people are considered entitled to fully avoid -- like pornography -- and there is content that people are considered obligated to consume -- like education.

And the issue is engrossingly complicated (if you're inclined to geek out about this sort of thing) -- what kind of enforcement does the right not to listen deserve? What should the rules be about content posted in public? What are the different kinds of public? (Outside on Main Street is different than the inside of the candy shop, the bar, the porn store...) Is there any right to control over the content display in private space?

And there's the issue of speech as a form of violence -- both in the broadcast sense of hate speech and the individual sense of harassment. In the case of the former, there's the legal concept of hate speech (although as far as I can tell, in the US hate speech only exists in case law). As for the latter, restraining orders have been upheld in defense of a right not to be contacted, even going as far as calling pokes on Facebook a violation.

I don't have any answers here for the mechanics of free speech. I just wanted to spend some time talking about the fact that there is literally no possible manifestation of the institution of free speech that doesn't require an elaborate set of narrowly defined specific exceptions.