My first thought on reading this article was "what would an rm for the web look like?". It seems that many of the commenters on that post had the same thought.
One possible way this could work is to set up a proxy that people can set in their browser. Then if they don't want to see a particular website any more, they can visit the "rm" website, enter the address of the website that they don't want to see any more and then it would be blocked by the proxy. The "rm" website should of course also provide some way to remove a site from the blocked list.
There are a few reasons why such a thing might be useful. There are a few "shock websites" out there which most people would not want to visit knowingly. It could significantly cut down on the number of instances of rickrolling and spyware infections. It could enable organizations to take control of their own web filtering needs rather than relying on some off-the-shelf solution which is bound to block some sites that it shouldn't. Of course it would be easy to circumvent, but that's not the point - the idea isn't to prevent people from seeing stuff they really want to see, it's to keep them honest and keep them from accidentally stumbling onto unsavory areas of the web.