Is your web site located in a bad neighborhood? Chances are that if you have a web site, the server that it is hosted upon is home to a few other sites. You may have little or no control over the content of those sites. You may not even be aware that those sites exist. It's possible that one of your neighbors might believe that they can exhibit humor, satire, irony, or parody on their pages. They may try to do so.
Imagine that one of your web neighbors decides to create a parody of a large corporation, and the reaction to that "exercise" in free speech is to have every single one of the sites on your server, and the other machines owned by your web host disconnected from the web by their backbone provider. Your host has lost its connection to the web, and so have you. The company that felt they were being defamed used a threat of an action under the Digital Millennium Copyright Act, which resulted in the backbone provider cutting off access to your site.
What exactly is the relationship between copyright law and defamation? Where does the line get crossed when parody is seen as defamation? Was the Digital Millennium Copyright Act meant to be used in this manner? See the Village Voice's article Dow v. Thing, subtitled A Free-Speech Infringement That's Worse Than Censorship.