The homepages of those Firefox extensions will be killed using SOPA. The main Firefox extension site hosted by Mozilla will be forced via SOPA threats to delist the extensions. Individual developers, if known, will be prosecuted with nuisance lawsuits.
Even putting all that aside, distributing a list of "patches" to DNS begs the question of who can update those patches and how do we know to trust them, resolution of competing lists, spam, etc.
But more importantly than all that - most takedown requests may not target small sites with their own DNS names at all, but rather be targeted at huge sites like youtube and facebook, threatening SOPA action to force them to remove individual pages and content. Like a super-DMCA. No alternate DNS patchlist or Freenet-like tool will solve that because the content will be actually gone.
And Freenet (I2P, Tor, etc etc) are not answers because this is mostly about removing media rich content or content that is accessed by many people, and those services can't effectively host something that requires a lot of bandwidth.
Referring, of course, to the proposed U.S. legislation which could cause severe damage to the Internet—at least, that's what a lot of people are saying. See, e.g., this Open Letter From Internet Engineers to the U.S. Congress (the first signatory listed is Vint Cerf). On Wikipedia, people including Jimbo Wales are discussing strategies as extreme as blanking the entire site (except for an explanatory message) to get people's attention, and thereby perhaps incite them to action, such as calling their Congressional representative.
I just happened to find out about all this a few hours ago, being someone who tries to avoid distractions like most kinds of news, so possibly others here with similar habits will appreciate having it called to ther attention. Or possibly they won't. But to those of you who possess relevant kinds of expertise:
(I think this subject can be discussed without political advocacy, in which I am mostly not at all interested anyway. It just looks like a practical problem to me.)
Edited to Add: I forgot to include a fourth bullet point:
It seems to have been assumed by many commenters, nevertheless.