I don't like 'Monopoly' because most people don't recognize that as a fundamental problem. In fact in the case of media, monopoly is assumed as necessary to provide you with what you want (hundred million dollar blockbuster films).
The key thing to focus on is the imbalance of power SOPA creates and how that will end up getting in the way of Uncle Art's evening entertainment. So far the shoplifting shutting down the store analogy is the most pointed I've heard, but still not a catch phrase.
I find the shoplifting analogy decent, but the main flaw I see is that it keeps the discussion framed around crimes being committed and what is the punishment. Even if the punishment is seen as really extreme, centuries of legislation have shown that being "tough on crime" is extremely popular.
My hope with the term 'Prohibition' is to turn it around and put the focus on the evil being done by the media companies. They want the government take away your rights, because they don't want to compete fair and square with web technologies.